Everyone one of us who owns an Alpha DSLR, no matter what model, knows (to a bigger or lesser amount) what the Dynamic Range Optimization or DRO Function is.
What some of you may not know is that the technology behind DRO isn't developed by Sony, but licenced from a company called Apical. Apical is a company that develops software used in cameras from major brands, including Sony, that aims to deliver photographs closer to the way we see them with our eyes.
Digital Photography Review has recently posted an article of an interview they did with Apical's managing director Michael Tusch, on which he explains what their software does and what was the reason they created it, along with visual examples of how DRO works better most of the time than using tonal curve adjustment in post-processing.
It's a very interesting read if you're curious about how DRO works, the principles behind it and when is advised to use it and when not to use it.
Feature: Apical dynamic range interview by Richard Butler
Showing posts with label How it works. Show all posts
Showing posts with label How it works. Show all posts
Thursday, March 19, 2009
Thursday, February 5, 2009
Exposure Compensation- Helping The Camera Out On Tricky Scenes
Normal behavior
Cameras usually measure light to render the scene in a way that everything or almost everything will be lit and properly exposed. The way they measure light is different than it is done professionally with the use of hand held light meters (This will be discussed in another article).
They take their information from the light that passes through the lens, and based on that, they calculate the proper exposure settings in any mode except Manual; and that is because in Manual you control the exposure values, therefore the light metering is up to you.
However, sometimes you will point the camera at scenes that will contain elements that will throw off the camera and will expose incorrectly.
Tricky scenes
The camera's in built light meter measures the light in a scene based on the light reflected from the subjects in it.
However, there are colors that absorb light, that bounce it off or absorb a part and reflect another.
The camera's metering system is based on the notion that almost all colors reflect roughly the same amount of light and it calculates exposure based on that.
However, it may have happened to you that you pointed your camera at a person with white clothes with plenty of light around it and the camera underexposed the image OR you pointed the camera at something mostly black or made up of a dark color and it overexposed the image. Or viceversa.
In the first case, there isnt enough light in the shot and in the second theres too much light and the colors look washed out.
At this point you either go postal on the camera, switch to Manual or fix the photo in post processing.
All of these options are valid (except go postal on the camera, maybe) but sometimes there isnt enough time to switch to Manual and retake the shot or you dont like sitting in front of a computer for hours fixing a shot that should have come up properly the first time.
Don't panic though, there is a way to fix it right away.
Exposure Compensation
That way is called Exposure Compensation.
By exposure its meant the amount of light that will reach the sensor when you press the shutter.
Compensation in this case means to increase or decrease a value or values in order to properly expose a picture.
The values that directly affect exposure are Shutter Speed, Aperture and ISO.
So, if you are in any mode (except Manual) and you point your camera at a subject with bright colors (such as white) or dark colors (like black), the camera will think the following:
Bright colors: There is too much light in the picture, so I must select a fast shutter speed, a small aperture or low ISO in order to avoid overexposing the shot.
Dark colors: There isnt enough light in the picture, so I must select a slow shutter speed, big aperture or high ISO in order to avoid underexposing the shot.
The problem is, under this logic, the camera will underexpose in bright colors or overexpose in dark colors most of the time. It may actually not do this or it may happen that under bright colors you actually need to overexpose a bit and in dark underexpose a bit.
It all depends on the subject, amount of light available and the exposure values.
Exposure Compensation is a function that allows you to shift the exposure values and tell the camera to over or underexpose as you consider necessary.
+/-
In all Alpha DSLRs (and even in the cameras made by other manufacturers) the Exposure Compensation is represented by a button with these symbols: +/-. Usually the button is split in two; black on the plus side and white on the minus side.
In the Alpha DSLRs, this button is found at the back of the camera near the viewfinder (A100/200/300/350) or near the shutter button (A700/900).
Exposure compensation scale is based on a scale of exposure values (EV), the plus side illuminates the image and the minus side darkens the image.
When you press this button, either you will get a exclusive screen for you to move the cursor up or down the scale or the scale will light up if you use the Quick Navi screen.
As with any scale, there is a middle ground, in this case is 0, which is always the exposure recommended by the camera.
In the LCD screen looks like this:
+/-
-3 I I -2 I I -1 I I 0 I I 1 I I 2 I I 3+
In the viewfinder it will look like this:
-2 o o -1 o o 0 o o 1 o o 2+
The A700/900 go to -3 or +3, the A100/200/300/350 go from -2 to +2.
If you own a A700/900 don't worry if the scale in the viewfinder wont go to -3 or +3, if you compensate beyond -2 or +2, the camera will compensate to the value you select. The value will be displayed in the viewfinder as you select it, it will disappear once you press the shutter button, but the camera will compensate to the value you select.
Now, you may wonder why the LCD and viewfinder have I or o's between the numbers. Those are the EV steps.
EV Steps
"And what are those?" you may ask.
As I said before, the scale used to compensate its called EV scale, and the units to measure light in that scale are called steps.
As you compensate in either side of the scale, the shutter speed, aperture or ISO values change, it may be just one, two or the three of them.
The point is, whenever one of these values changes, the exposure changes.
The Alpha DSLRs have two ways of measuring in the EV scale: in 0.3 or 0.5 steps.
The A100/200/300/350 have their scales in 0.3 EV steps and the A700/900 can deal with 0.3 or 0.5 EV steps.
The I's in the LCD between the numbers or the o's in the viewfinder between numbers are the markers when you measure in 0.3 EV steps, but when you measure in 0.5 EV steps, the marker is placed between two I's or two o's.
0.3, 0.5, 0.7
So what's the difference between 0.3 and 0.5 EV steps?
The basic difference is the amount of steps you can compensate.
In 0.3 steps, the scale goes like this:
-3, -2.7, -2.3, -2.0, -1.7, -1.3, -1. -0.7, -0.3, 0, +0.3, +0.7, +1.0, +1.3, +1.7, +2.0. +2.3, +2.7, +3
In 0.5 EV steps, the scale goes like this:
-3, -2.5, -2.0, -1.5, -1.0, -0.5, 0, +0.5, +1.0, +1.5, +2.0, +2.5, +3.0
When you use 0.3 EV steps, the scale is larger because you can access 0.3 and 0.7 steps of compensation between numbers.
When you use 0.5 EV steps, you can only access halves between each number. The scale is smaller.
Differences between 0.3 and 0.5 EV steps
Now, if you use a A100/200/300/350, you dont have to worry about 0.5 EV steps because you can't access them, but if you want to know the difference between 0.3 and 0.5 scales, keep reading.
For those of you using a A700/900, there are differences when you use 0.3 or 0.5 EV step scales.
The use of both scales presents tradeoffs. Using a 0.3 EV step scale allows you to use a bigger scale whereas 0.5 is more limited.
The difference is that if you need precise increments, 0.5 EV works a lot better than 0.3 EV, because 0.3 EV presents you subtle changes that wont affect too much the exposure in case you screw up, but it will require you to use more steps to make a visible compensation. And thats another tradeoff, if you want subtle changes without introducing a harsh change in exposure, 0.5 EV wont work for you since that's what it will do, the changes will be more visible, so if you want just a slight touch of more light into the picture, 0.5 EV won't do the job since it will introduce more light in each step than 0.3 EV.
In 0.3 EV, the lack of a middle point between steps is compensated by the fact that you can use 0.7 EV as well, and that step may introduce enough light to make a difference or a little too much. It all depends on the scene.
In 0.5 EV the changes are more predictable, so if you require a visible change and you know how much, 0.5 EV will work better than 0.3 EV since it won't require you to decide whether to use a 0.3 or 0.7 step compensation, it will be just a half and you can learn what to expect. However, if you rather make exposures where the light is increased or decreased in a more gradual manner, chose 0.3 EV.
There is one more thing to keep in mind: the scale you chose for Exposure Compensation also affects the shutter speed and aperture range. If you chose 0.3 EV, the shutter speed and aperture will change in values of 1/3rd whereas if you chose 0.5 EV, the values will change in halves.
This is done in order to match the changes introduced in 0.3 or 0.5 EV steps.
And again, there is a tradeoff, having the speed or aperture shown in 1/3rd gives you a broader range of speed and aperture (limited by your camera's top speed or lens' aperture range) but it will take longer for you to get to the setting you want, which wont happen if you use 0.5 EV.
It's up to you which scale you use; 0.3 or 0.5 EV.
To change between those two in the A700: Menu-> Recording Menu (camera icon) Page 1-> Exposure step-> 0.3 or 0.5 EV
In the A900: Menu-> Recording Menu (camera icon) Page 2-> Exposure Step-> 0.3 or 0.5 EV
Notes of use and Closure
Cameras usually measure light to render the scene in a way that everything or almost everything will be lit and properly exposed. The way they measure light is different than it is done professionally with the use of hand held light meters (This will be discussed in another article).
They take their information from the light that passes through the lens, and based on that, they calculate the proper exposure settings in any mode except Manual; and that is because in Manual you control the exposure values, therefore the light metering is up to you.
However, sometimes you will point the camera at scenes that will contain elements that will throw off the camera and will expose incorrectly.
Tricky scenes
The camera's in built light meter measures the light in a scene based on the light reflected from the subjects in it.
However, there are colors that absorb light, that bounce it off or absorb a part and reflect another.
The camera's metering system is based on the notion that almost all colors reflect roughly the same amount of light and it calculates exposure based on that.
However, it may have happened to you that you pointed your camera at a person with white clothes with plenty of light around it and the camera underexposed the image OR you pointed the camera at something mostly black or made up of a dark color and it overexposed the image. Or viceversa.
In the first case, there isnt enough light in the shot and in the second theres too much light and the colors look washed out.
At this point you either go postal on the camera, switch to Manual or fix the photo in post processing.
All of these options are valid (except go postal on the camera, maybe) but sometimes there isnt enough time to switch to Manual and retake the shot or you dont like sitting in front of a computer for hours fixing a shot that should have come up properly the first time.
Don't panic though, there is a way to fix it right away.
Exposure Compensation
That way is called Exposure Compensation.
By exposure its meant the amount of light that will reach the sensor when you press the shutter.
Compensation in this case means to increase or decrease a value or values in order to properly expose a picture.
The values that directly affect exposure are Shutter Speed, Aperture and ISO.
So, if you are in any mode (except Manual) and you point your camera at a subject with bright colors (such as white) or dark colors (like black), the camera will think the following:
Bright colors: There is too much light in the picture, so I must select a fast shutter speed, a small aperture or low ISO in order to avoid overexposing the shot.
Dark colors: There isnt enough light in the picture, so I must select a slow shutter speed, big aperture or high ISO in order to avoid underexposing the shot.
The problem is, under this logic, the camera will underexpose in bright colors or overexpose in dark colors most of the time. It may actually not do this or it may happen that under bright colors you actually need to overexpose a bit and in dark underexpose a bit.
It all depends on the subject, amount of light available and the exposure values.
Exposure Compensation is a function that allows you to shift the exposure values and tell the camera to over or underexpose as you consider necessary.
+/-
In all Alpha DSLRs (and even in the cameras made by other manufacturers) the Exposure Compensation is represented by a button with these symbols: +/-. Usually the button is split in two; black on the plus side and white on the minus side.
In the Alpha DSLRs, this button is found at the back of the camera near the viewfinder (A100/200/300/350) or near the shutter button (A700/900).
Exposure compensation scale is based on a scale of exposure values (EV), the plus side illuminates the image and the minus side darkens the image.
When you press this button, either you will get a exclusive screen for you to move the cursor up or down the scale or the scale will light up if you use the Quick Navi screen.
As with any scale, there is a middle ground, in this case is 0, which is always the exposure recommended by the camera.
In the LCD screen looks like this:
+/-
-3 I I -2 I I -1 I I 0 I I 1 I I 2 I I 3+
In the viewfinder it will look like this:
-2 o o -1 o o 0 o o 1 o o 2+
The A700/900 go to -3 or +3, the A100/200/300/350 go from -2 to +2.
If you own a A700/900 don't worry if the scale in the viewfinder wont go to -3 or +3, if you compensate beyond -2 or +2, the camera will compensate to the value you select. The value will be displayed in the viewfinder as you select it, it will disappear once you press the shutter button, but the camera will compensate to the value you select.
Now, you may wonder why the LCD and viewfinder have I or o's between the numbers. Those are the EV steps.
EV Steps
"And what are those?" you may ask.
As I said before, the scale used to compensate its called EV scale, and the units to measure light in that scale are called steps.
As you compensate in either side of the scale, the shutter speed, aperture or ISO values change, it may be just one, two or the three of them.
The point is, whenever one of these values changes, the exposure changes.
The Alpha DSLRs have two ways of measuring in the EV scale: in 0.3 or 0.5 steps.
The A100/200/300/350 have their scales in 0.3 EV steps and the A700/900 can deal with 0.3 or 0.5 EV steps.
The I's in the LCD between the numbers or the o's in the viewfinder between numbers are the markers when you measure in 0.3 EV steps, but when you measure in 0.5 EV steps, the marker is placed between two I's or two o's.
0.3, 0.5, 0.7
So what's the difference between 0.3 and 0.5 EV steps?
The basic difference is the amount of steps you can compensate.
In 0.3 steps, the scale goes like this:
-3, -2.7, -2.3, -2.0, -1.7, -1.3, -1. -0.7, -0.3, 0, +0.3, +0.7, +1.0, +1.3, +1.7, +2.0. +2.3, +2.7, +3
In 0.5 EV steps, the scale goes like this:
-3, -2.5, -2.0, -1.5, -1.0, -0.5, 0, +0.5, +1.0, +1.5, +2.0, +2.5, +3.0
When you use 0.3 EV steps, the scale is larger because you can access 0.3 and 0.7 steps of compensation between numbers.
When you use 0.5 EV steps, you can only access halves between each number. The scale is smaller.
Differences between 0.3 and 0.5 EV steps
Now, if you use a A100/200/300/350, you dont have to worry about 0.5 EV steps because you can't access them, but if you want to know the difference between 0.3 and 0.5 scales, keep reading.
For those of you using a A700/900, there are differences when you use 0.3 or 0.5 EV step scales.
The use of both scales presents tradeoffs. Using a 0.3 EV step scale allows you to use a bigger scale whereas 0.5 is more limited.
The difference is that if you need precise increments, 0.5 EV works a lot better than 0.3 EV, because 0.3 EV presents you subtle changes that wont affect too much the exposure in case you screw up, but it will require you to use more steps to make a visible compensation. And thats another tradeoff, if you want subtle changes without introducing a harsh change in exposure, 0.5 EV wont work for you since that's what it will do, the changes will be more visible, so if you want just a slight touch of more light into the picture, 0.5 EV won't do the job since it will introduce more light in each step than 0.3 EV.
In 0.3 EV, the lack of a middle point between steps is compensated by the fact that you can use 0.7 EV as well, and that step may introduce enough light to make a difference or a little too much. It all depends on the scene.
In 0.5 EV the changes are more predictable, so if you require a visible change and you know how much, 0.5 EV will work better than 0.3 EV since it won't require you to decide whether to use a 0.3 or 0.7 step compensation, it will be just a half and you can learn what to expect. However, if you rather make exposures where the light is increased or decreased in a more gradual manner, chose 0.3 EV.
There is one more thing to keep in mind: the scale you chose for Exposure Compensation also affects the shutter speed and aperture range. If you chose 0.3 EV, the shutter speed and aperture will change in values of 1/3rd whereas if you chose 0.5 EV, the values will change in halves.
This is done in order to match the changes introduced in 0.3 or 0.5 EV steps.
And again, there is a tradeoff, having the speed or aperture shown in 1/3rd gives you a broader range of speed and aperture (limited by your camera's top speed or lens' aperture range) but it will take longer for you to get to the setting you want, which wont happen if you use 0.5 EV.
It's up to you which scale you use; 0.3 or 0.5 EV.
To change between those two in the A700: Menu-> Recording Menu (camera icon) Page 1-> Exposure step-> 0.3 or 0.5 EV
In the A900: Menu-> Recording Menu (camera icon) Page 2-> Exposure Step-> 0.3 or 0.5 EV
Notes of use and Closure
- The primary function of Exposure compensation is to illuminate or darken an image when the camera doesn't expose correctly because its pointed at a subject or scene mostly made of white or black.
- Exposure Compensation is useful, especially since Auto Mode tends to underexpose sometimes.
- It must be used with caution since it can ruin a photo if not used properly. Use only as much as you need to get the shot you want, if you over do it in any part, you may do a worse mess than the camera's.
- For pictures that require a drastic and precise compensation, use 0.5 EV, for pictures that require subtle and gradual changes use 0.3 EV.
- It doesn't work in Manual Mode, but will work in the rest of the modes, even Scene Modes.
- In Manual Mode, the Exposure Compensation scale changes to M.M.; which means Metered Manually, the camera still offers its opinion about the proper exposure to chose but the final choice its up to you and you can ignore the camera's recommendation.
- There is more range in compensation in 0.3 EV than in 0.5 EV, but in 0.5 EV the changes are more visible in each step.
- For some weird reason, in the A700 happened that when using Exposure Compensation; the exposure values DIDN'T change BUT the illumination in the picture DID change a bit.
Exposure Compensation is a useful tool when you're shooting in P,A,S or any Scene Mode (except in the A900, it doesn't have Scene Modes) and the shots aren't coming properly exposed. It allows you to do a quick tuning and let the camera do the rest, you just tell it how bright or dark you want the picture to be regardless of what it thinks.
This function will save you time in front of your computer and will give you more time to take more pictures.
One final advice: I strongly recommend you conduct experiments of your own with this function so you learn the changes it introduces in a picture and how does the camera behave when you use it, this way you will learn to know what to expect from this function and will give you a solid idea of how much to use and when to use it.
Friday, January 23, 2009
Product Review: Sensor Klear Cleaning System
An apology for the long delay in bringing you this article, Ive been busy and I couldn't work on it, but here it is now.
Introduction
One of the most important parts of your camera is the sensor.
The sensor is the part that work like film does in SLRs. It's the part that captures the image your lens is seeing.
However, unlike film, the sensor is fixed on its position, and its prone to get dirty.
Ever since the beginning of the digital age in photography, sensors have been getting dirty and it was a problem that camera makers addressed by implementing filters and vibrating mechanism to remove dust that attaches.
However, sometimes that's not enough and a more thorough cleaning is needed. This article will review a product that will help you clean your sensor in an easy and safe way.
How does a sensor gets dirty?
If you use a DSLR, eventually you will get your sensor dirty. Theres no way to avoid it.
Unlike P&S cameras that have their sensor locked and sealed within the body, DSLRs have it exposed, being protected only by the shutter. The sensor per se isn't exposed, you can see it, but in front of it, there is a filter that protects it. This filter is the one who catches dust and other contamination.
The first DSLRs didn't have any filter in front of the sensor, so if dust was around, the sensor itself caught it, which posed a problem when cleaning since there is dust that will go away with a blower and dust that will require more effort to remove. The dust that didn't go away with a blow could end up scratching the sensor, rendering it useless.
All the Sony Alpha DSLRs (A100/200/300/350/700/900) have a filter in front of the sensor, so there is no risk of ruining your sensor per se.
Dust is the most common form of contamination that a sensor can experience.
Every time you change your lens, the mirror chamber is exposed. Behind the mirror, there is the shutter (those black curtains that move when you take a picture), behind those curtains, there is the sensor.
The camera runs an electrical current through all of it in order to function, this includes the lens. The movement of parts (mirror, shutter, AF mechanism, etc.) generates static electricity.
This electricity attracts dust, dust is sensitive to this kind of electricity. If dust enters in the mirror box, its prone to attach to the filter in front of the sensor once the shutter opens to take a picture.
Since the sensor is running a current and the shutter curtains move, the dust has it easy to stick to it.
In theory, dust is the only contamination your sensor should experience, unless you wet it with something or stick something to it. Read this article for more information about it.
Introduction
One of the most important parts of your camera is the sensor.
The sensor is the part that work like film does in SLRs. It's the part that captures the image your lens is seeing.
However, unlike film, the sensor is fixed on its position, and its prone to get dirty.
Ever since the beginning of the digital age in photography, sensors have been getting dirty and it was a problem that camera makers addressed by implementing filters and vibrating mechanism to remove dust that attaches.
However, sometimes that's not enough and a more thorough cleaning is needed. This article will review a product that will help you clean your sensor in an easy and safe way.
How does a sensor gets dirty?
If you use a DSLR, eventually you will get your sensor dirty. Theres no way to avoid it.
Unlike P&S cameras that have their sensor locked and sealed within the body, DSLRs have it exposed, being protected only by the shutter. The sensor per se isn't exposed, you can see it, but in front of it, there is a filter that protects it. This filter is the one who catches dust and other contamination.
The first DSLRs didn't have any filter in front of the sensor, so if dust was around, the sensor itself caught it, which posed a problem when cleaning since there is dust that will go away with a blower and dust that will require more effort to remove. The dust that didn't go away with a blow could end up scratching the sensor, rendering it useless.
All the Sony Alpha DSLRs (A100/200/300/350/700/900) have a filter in front of the sensor, so there is no risk of ruining your sensor per se.
Dust is the most common form of contamination that a sensor can experience.
Every time you change your lens, the mirror chamber is exposed. Behind the mirror, there is the shutter (those black curtains that move when you take a picture), behind those curtains, there is the sensor.
The camera runs an electrical current through all of it in order to function, this includes the lens. The movement of parts (mirror, shutter, AF mechanism, etc.) generates static electricity.
This electricity attracts dust, dust is sensitive to this kind of electricity. If dust enters in the mirror box, its prone to attach to the filter in front of the sensor once the shutter opens to take a picture.
Since the sensor is running a current and the shutter curtains move, the dust has it easy to stick to it.
In theory, dust is the only contamination your sensor should experience, unless you wet it with something or stick something to it. Read this article for more information about it.
Effects of dust in a sensor
All camera makers do not want you to futz with the sensor if it gets dirty so you wont break or ruin your camera. The most recommended solution is to blow air into the sensor to remove it.
But there is dust that wont go away with a blow (and by blow I mean using a blower to do so, not your mouth since you can spit over the sensor).
So what happens when you have dust on your sensor?
The thing with dust is that you wont notice it if you use large apertures such as f/1.4, 2.0, 2.8, 3.5 and so forth. Since light is splattered all over the sensor, it conceals the dust.
However, if you close your lens up to f/11, 16, 22, 32, 40 and so, you will start to notice dark spots on your pictures. In a closed down lens, light is fed to the sensor in a more precise way, so if there is something in front of it, it will come out in the picture.
You can either use large apertures to avoid dust from coming out on the shot or clean your sensor.
Ignoring the issue is easier than doing something about it, but keep in mind this: If you ever require to use a small aperture in order to have as much Depth Of Field as possible or your camera selects a small aperture, your shot will show dust spots and you will have to waste time removing them with post processing software.
It's far better to deal with the issue so you have your whole aperture range at your disposal and not limited.
Cleaning methods
There are a thousand different ways to clear your sensor, some are just plain silly and will leave a worse mess than you originally had, some are very effective but require precise movements and time and above all, skill.
As Ive stated before, here in Alpha Sight the axiom I follow regarding cleaning sensors is:
IF YOU DO NOT TRUST YOURSELF OR DO NOT FEEL CONFIDENT ENOUGH TO DO A CLEANING PROCEDURE, DO NOT DO IT. TAKE YOUR CAMERA TO AN AUTHORIZED SERVICE CENTER OR LET A QUALIFIED PERSON TO DO IT.
This is in order to avoid that you make things worse or ruin your equipment for good when trying to clean it.
The scope of sensor cleaning is vast and wide, this article will focus only in one. If you would like to learn more about other sensor cleaning methods, check out the links at the right side of this blog, ask in photography forums, and surf the net. There are plenty of answers out there.
Finally, if you rather leave this in expert hands, you can look for a Sony Authorized Service Center or take it to Adorama or Calumet Photo.
If you want to learn an easy way to clean your sensor, keep reading.
The Sensor Klear by LensPen
If you read the previous article, you will see a review of a cleaning product for lenses called LensPen.
Well, the company that produces that item, also produces items to clean other camera parts, including the sensor.
Their product is called Sensor Klear.
The Sensor Klear is similar to its LensPen cousin, its the size of a pen, although a bit smaller and thinner than the classical LensPen.
It's made of a retractable brush and a cleaning tip with the same carbon based compound that the LensPen has. For those of you who don't know, the tip is made of carbon, similar to the one found in pencils or in the ink of newspapers. The ink contains carbon, and the carbon absorbs impurities.
Unlike other methods (like the wet one) that require flammable fluids or tissues or swabs, the Sensor Klear doesn't create waste. And it's safe to take it on planes, whereas the liquids used for cleaning sensors with the wet method aren't allowed.
The cleaning tip of the Sensor Klear is smaller than the one in the LensPen, but there is a reason for that; it gives you more control over the handling of the tip when you clean the sensor.
Whereas on a lens you have a broad space to work with, on a sensor is different, you got to be careful not to mess with other components inside the mirror box. Having a smaller cleaning tip allows you to move the Sensor Klear just enough to clean the sensor and avoiding touching something else.
There is another feature to the Sensor Klear's cleaning tip: its in a triangular shape. This is done to allow you to clean the corners of the sensor if its required, if it had been a circular shape, you wouldnt reach the farthest corners of the sensor, and if you got dust there, it would be a problem.
To maximize the usefulness of the Sensor Klear, the head bends in order to give you flexibility in case you need to move the pen in an angle.
How to use it
1.- Set the camera to Cleaning Mode
In the A100: Menu-> Setup (Wrench Icon) Page 3-> Clean CCD
A200/300/350: Menu-> Setup (Wrench Icon) Page 3-> Cleaning Mode
A700: Menu-> Setup (Wrench Icon) Page 3-> Cleaning Mode
A900: Menu-> Setup (Wrench Icon) Page 3-> Cleaning Mode
Cleaning Mode (or Clean CCD) locks the mirror up, opens the shutter and cuts power off the sensor for you to clean it.
DO NOT NOT NOT NOT NOT USE BULB SHUTTER SPEED UNDER ANY CIRCUMSTANCE.
This is risky AND stupid. Bulb is designed for long exposures NOT sensor cleaning. While its true that it opens the shutter and reveals the sensor as long as you keep the shutter button pressed, IT DOES NOT LOCK THE MIRROR UP NOR IT CUTS POWER OFF THE SENSOR, IF YOU ACCIDENTALLY REMOVE YOUR FINGER OFF THE SHUTTER BUTTON AND IT CLOSES, THE SHUTTER CURTAINS CAN CRASH AGAINST THE SENSOR KLEAR AND THEY WILL GET BENT, THIS MEANS YOUR CAMERA IS RUINED FOR GOOD.
DO NOT USE BULB SHUTTER SPEED, USE CLEANING MODE.
2.- Remove the lens mounted on the camera and put it aside where its safe.
3.- Hold the camera body firmly and position it in a downward angle to prevent dust or other materials from entering the mirror box.
4.- Use the retractable brush on the Sensor Klear to remove any dust on the lens mount. Make sure you retract it back when you're done with it.
5.- Use a high quality air blaster to blow away dry and easy-to-remove dust from the sensor.
Note: It may happen that by doing this, the dust particles on your sensor may be blown away and that's it, no more cleaning required. However, make sure you don't blow the dust into the mirror or inside the viewfinder. If it lands on the mirror, use the brush gently to remove it. You will only notice if its on the mirror or the viewfinder once you turn the camera OFF and the mirror comes back down and you look through the viewfinder. If you see spots, its in one of those two. Blow or brush it away. Keep in mind that dust in those places WILL NOT show up in the picture.
6.- Use the Sensor Klear's cleaning tip to remove any dust, stains or oil from the sensor. Play close attention to the corners. If you used a blower, dust may have moved to the corners and hide there.
7.- Once you're done, put the cap back on the cleaning tip and give it two twists to leave it ready for next time.
8.- Use the brush to remove dust from the rear element in your lens if there's any. If you see finger prints or something else, you will need a LensPen to remove it.
The cleaning tip
Inside the cap, you will find a foam pad, that is the replenisher that contains the carbon compound, everytime you use the Sensor Klear make sure to put the cap back on and give it two twists to replenish the cleaning tip for next time you need to clean the sensor.
Notes of use
Here are some points to keep in mind when using the Sensor Klear:
- It's possible that one pass with the Sensor Klear won't do. Sometimes dust is sticky and requires more passes to remove. Keep using the Sensor Klear until the sensor is completely clean.
- The test to find dust on your sensor is: Point the camera to a white piece of paper or at the sky at infinity focus, select f/22 or a smaller aperture and take a picture. If there are spots, there is dust. When you clean your sensor perform this test to confirm your sensor is clean or if there are still spots to be removed.
- It's possible that you clean dust on one part of the sensor and it shows up on another part. If this happens, do a thorough cleaning of the whole sensor to ensure that no dust is left behind or just moved.
- Again, DO NOT USE BULB SHUTTER SPEED, USE CLEANING MODE.
- Do NOT use the brush to clean the sensor, use only the cleaning tip.
- The Sensor Klear lasts 50 uses.
- There are replaceable heads in case you use it 50 times, you just pull the tip off and insert the new one.
- The Sensor Klear is advertised to work with CCD sensors, it also works with CMOS sensors.
- DO NOT TOUCH THE BRUSH WITH YOUR FINGERS, YOU MAY ADD SKIN OILS TO IT AND IT WILL STREAK WHATEVER SURFACE YOU USE IT ON.
- DO NOT TOUCH THE CLEANING TIP WITH YOUR FINGERS EITHER.
- When using it, do NOT press hard against the sensor or the mirror, you may disalign them and that is B-A-D.
- It's recommended that you use a clean environment with no breezes.
- I recommend using a strong light and a magnifying glass to see what youre doing. The company that produces the Sensor Klear is about to release a magnifying glass designed for sensor cleaning as well.
- Use latex gloves and a gown if possible, this will reduce the chance you will touch something you shouldnt and ruin it or breathe or sneeze over the mirror box and/or sensor.
- Do NOT blow the sensor with your mouth, your breath contains saliva, which may end up falling over the sensor. If it does, use the cleaning tip.
- DO NOT USE CANNED AIR UNDER ANY CIRCUMSTANCE. Canned air has been proved to contain all sorts of particles on it and you may end up giving those to your sensor.
- The Sensor Klear is environmentally friendly, it doesnt create waste nor it requires flammable liquids, swabs, tissues, etc.
- The Sensor Klear reduces static build up on your sensor, this will help to reduce the amount of dust being pulled towards your sensor.
- A blower is recommended with this product because sometimes dust will go away before you use the Sensor Klear.
- Clean your sensor only when necessary, check for dust every month and remove it as soon as you find it, the longer dust stays there, the harder it is to remove.
- Finally and again: IF YOU DO NOT TRUST YOURSELF OR DO NOT FEEL CONFIDENT ENOUGH TO DO A CLEANING PROCEDURE, DO NOT DO IT. TAKE YOUR CAMERA TO AN AUTHORIZED SERVICE CENTER OR LET A QUALIFIED PERSON TO DO IT.
Links
Official Site
Sensor Klear
How to use the Sensor Klear presentation
Link to purchase it through Amazon
Closure
Sensor cleaning is a tricky business. If done well, it's not an issue, but for the inexperienced it can be something terrifying to do.
Methods to do it there are by the boat load, but the few that really work need practice and skill.
The Sensor Klear is an easy way to clean your sensor quickly and with no hassle if done correctly.
To have a dirty sensor these days can be a problem, especially if youre not aware of it. It may present a problem when you least expect it and you will need to waste time removing dust spots from your pictures in post processing.
You may ignore the issue using large apertures, but like I said, one day you will need to use a small f/stop and you will be in trouble.
The Sensor Klear is a method that works everywhere and you can always take it with you since it doesnt take much space at all. And the procedure is really simple and doesnt require special liquids or swabs or whatever. You can travel with it since its completely safe.
This product is therefore, an Alpha Sight recommended product.
Finally, if you purchase this item and you've never cleaned a sensor before, read this whole article again, read this article as well too. Read and watch the presentation at the official site. If you have any questions, you're always welcome to ask me.
And remember, if you dont feel confident enough to clean your sensor, DON'T, leave it to someone who does know what he is doing.
Until next time.
Thursday, January 8, 2009
Product Review: LensPen Cleaning System
On this article, I will review an item for lens cleaning Ive personally used: The LensPen cleaning system.
Introduction
As I mentioned before, your lens is bound to get dirty at some point, unless you use a protective filter. In that case, the filter will get dirty instead of the lens, but the fact remains that something will get dirty.
There are very common procedures to clean a lens when it gets dirty, but theres the risk you may end up doing a worse mess with them.
In my interest of preventing that a mess happens to you, Im bringing you this review you may want to consider if you need a fast, easy and safe lens cleaning option
The LensPen
Recently I used a product called LensPen to clean my Sony 18-200mm that had some liquid stains and dust on the front element and a Kenko special filter that required a good cleaning.
The LensPen is a device the size of a pen (ergo the last suffix on the name, duh :) ) which has a retractable brush on one side and a cleaning tip on the other one.
Unlike other cleaning products, the LensPen doesnt pose a threat to the lens' glass nor will it make things worse. It's proven to remove finger prints and leave no trace of them.
The LensPen works under the same concept used by people who clean glass with newspapers. Newspapers have ink, which in turn contains carbon, carbon absorbs impurities and removes them without leaving marks.
The LensPen cleaning tip contains a carbon compound that removes skin oils and other stains on your lens without leaving any marks. The brush on the other side is designed to remove dust and other lose particles that can be easily removed.
The cleaning tip is flexible, which allows you to reach the edges of the lens easily, the brush is retractable, keeping it safe from getting damaged while transporting it or from your fingers.
It's portable since it doesnt take too much space, easy to use and safe for your lenses.
How to use it
Introduction
As I mentioned before, your lens is bound to get dirty at some point, unless you use a protective filter. In that case, the filter will get dirty instead of the lens, but the fact remains that something will get dirty.
There are very common procedures to clean a lens when it gets dirty, but theres the risk you may end up doing a worse mess with them.
In my interest of preventing that a mess happens to you, Im bringing you this review you may want to consider if you need a fast, easy and safe lens cleaning option
The LensPen
Recently I used a product called LensPen to clean my Sony 18-200mm that had some liquid stains and dust on the front element and a Kenko special filter that required a good cleaning.
The LensPen is a device the size of a pen (ergo the last suffix on the name, duh :) ) which has a retractable brush on one side and a cleaning tip on the other one.
Unlike other cleaning products, the LensPen doesnt pose a threat to the lens' glass nor will it make things worse. It's proven to remove finger prints and leave no trace of them.
The LensPen works under the same concept used by people who clean glass with newspapers. Newspapers have ink, which in turn contains carbon, carbon absorbs impurities and removes them without leaving marks.
The LensPen cleaning tip contains a carbon compound that removes skin oils and other stains on your lens without leaving any marks. The brush on the other side is designed to remove dust and other lose particles that can be easily removed.
The cleaning tip is flexible, which allows you to reach the edges of the lens easily, the brush is retractable, keeping it safe from getting damaged while transporting it or from your fingers.
It's portable since it doesnt take too much space, easy to use and safe for your lenses.
How to use it
- Begin by removing any dust or lose particles on the front element. For this you have to use the retractable brush.
- Remove the cap covering the cleaning tip and wipe the lens with smooth and circular movements with the tip. If there are smudges or stains that persist, you can breathe gently on the lens and repeat the process. (Believe it or not, this works, tried this myself)
- Put the cap over the cleaning tip again and give the cap a half twist to replenish the cleaning tip.
The cleaning tip
The cleaning tip is what contains the carbon compound that cleans the glass surface. Inside the cap you will find a foam pad, which is the replenisher. Everytime you use the LensPen, you have to replenish the tip to keep it working.
Notes of use
Here are some things to keep in mind when using/about the LensPen:
- The LensPen is designed to work with camera lenses, videocamera lenses and small camera lenses, rifle scopes, microscopes, night vision googles, telescopes, etc.
- The LensPen has a life of 500 uses (Although it may vary depending on what kind of contamination is present on your lens)
- Do NOT use it on wet surfaces
- The LensPen is environmentally friendlier than other cleaning methods since it wont require solvents or other liquids, tissues and creates no waste.
- The LensPen isnt exactly designed to clean eyeglasses due to the fact that eyeglasses have concave and convex design, but you can give it a shot.
- DO NOT TOUCH THE CLEANING TIP OR THE BRUSH WITH YOUR FINGERS
- In order to prevent the previous point from happening, use gloves when using it
- The compound will not spill or dry out
- The LensPen is reported to reduce electrostatic charge. (This is a cool feature, because electrostatic charge is the thing that says to dust: Hey , over here!. If you wonder how can a lens can get static electricity, heres how: by moving it, when it gets rubbed in transport, when plugged to a camera)
- The LensPen may leave a black mark on your finger but not on the lens, this is because of the carbon compund. Like the lead found in pencils.
- If there an excess of cleaning compound on the tip, it may leave traces of it on the lens. This is fixable by blowing the compound away from the lens with an air blaster and patting the tip on a soft cloth.
- The official site says there are some bogus LensPens out there not made by the official company. To know if your LensPen is legit or not look for the words: "Distributed under the authority of Parkside Optical Inc., Vancouver, Canada" and the official hologram on the backcard.
- If you need the clean a small lens, you should consider the MiniPro LensPen which is designed for smaller lenses.
Links
Comparision with other systems
How to use the LensPen and Information presentation
Link to purchase it through Amazon
The LensPen is a cheap and easy solution to clean your lenses when they get dirty. Since its portable, you can take it with you without worrying about space in your bag.
Having clean equipment has become critical and practically a necessity for photographers everywhere, the option of being able to do it immediately give this method a huge advantage over other systems. Theres also the fact that you dont touch the cleaning element with your hands, as you do with tissues or cloths.
This product is therefore, an Alpha Sight recommended product.
Coming up next, a product to easily clean your sensor: the Sensor Klear.
Saturday, December 13, 2008
Lenses-How To Pick One And Read Their Specs: Part 3
Technical data not explained in a lens explained
Lens groups/elements: A lens may seem to be built in a complex way, but in reality its made up of smaller lenses inside it called simple lenses. These lenses are shaped in a specific form so they will create the effect required. When packed together inside the lens, they combine to make the lens you end up holding.
The arrangement of these simple lenses can be in groups or by their own, depending on the lens construction and what kind of lens it is. Each simple lens is called element and a group of simple lenses its called lens group.
When you buy a lens, in the technical specifications its stated how much lens groups and/or elements the lens is made of. Depending on the maker, a lens may contain little or a lot of elements inside it.
Minimum focus distance: In order to bring things in focus, a lens needs to have the proper distance from the subject. There is a limit to how far or how near the subject needs to be from the lens in order to be in focus. The minimum focusing distance is how much distance there HAS to be between your subject and your lens in order to be properly focused. If you dont have this distance, you wont be able to focus.
Unlike high end P&S cameras that require a lot less minimum focusing distance, DSLRS require more, this is determined by what kind of lens youre using and the size of your sensor. Since P&S cameras have a much smaller sensor, they have a much more cropped view, so close ups can be done with the lens practically over your subject.
The only lenses in DSLR system that can do close ups from really close to your subject are macro lenses. The minimum focusing distance varies from lens to lens, its not the same or standard among them, only if you own two identical lenses.
It's important to know this distance for every lens youve got so you know how close you can physicially get to your subject before the lens can't focus. It will spare you of losing moments you may not get back.
Filter diameter: Almost all lenses have a marking in them that tells you what size the front element is so you can attach a filter. The symbol is this one: Ø. This symbol comes with a number. In the Sony 28mm f/2.8 it comes like this: Ø 49mm. This means that if you want to attach a filter to this lens, you need a 49mm sized filter. The Sony 18-200mm f/3.5-6.3 shows Ø 62mm. The lens is bigger than the 28mm, therefore it requires a 62mm filter.
Since lenses vary in size, they size of filters you will need changes a lot. This makes it a problem if you want to put filters on all your lenses, since the variance in sizes may result in one filter being more expensive than others due to rare size or lack of filters due to the size.
Whenever you plan to attach a filter keep in mind two things:
Lens groups/elements: A lens may seem to be built in a complex way, but in reality its made up of smaller lenses inside it called simple lenses. These lenses are shaped in a specific form so they will create the effect required. When packed together inside the lens, they combine to make the lens you end up holding.
The arrangement of these simple lenses can be in groups or by their own, depending on the lens construction and what kind of lens it is. Each simple lens is called element and a group of simple lenses its called lens group.
When you buy a lens, in the technical specifications its stated how much lens groups and/or elements the lens is made of. Depending on the maker, a lens may contain little or a lot of elements inside it.
Minimum focus distance: In order to bring things in focus, a lens needs to have the proper distance from the subject. There is a limit to how far or how near the subject needs to be from the lens in order to be in focus. The minimum focusing distance is how much distance there HAS to be between your subject and your lens in order to be properly focused. If you dont have this distance, you wont be able to focus.
Unlike high end P&S cameras that require a lot less minimum focusing distance, DSLRS require more, this is determined by what kind of lens youre using and the size of your sensor. Since P&S cameras have a much smaller sensor, they have a much more cropped view, so close ups can be done with the lens practically over your subject.
The only lenses in DSLR system that can do close ups from really close to your subject are macro lenses. The minimum focusing distance varies from lens to lens, its not the same or standard among them, only if you own two identical lenses.
It's important to know this distance for every lens youve got so you know how close you can physicially get to your subject before the lens can't focus. It will spare you of losing moments you may not get back.
Filter diameter: Almost all lenses have a marking in them that tells you what size the front element is so you can attach a filter. The symbol is this one: Ø. This symbol comes with a number. In the Sony 28mm f/2.8 it comes like this: Ø 49mm. This means that if you want to attach a filter to this lens, you need a 49mm sized filter. The Sony 18-200mm f/3.5-6.3 shows Ø 62mm. The lens is bigger than the 28mm, therefore it requires a 62mm filter.
Since lenses vary in size, they size of filters you will need changes a lot. This makes it a problem if you want to put filters on all your lenses, since the variance in sizes may result in one filter being more expensive than others due to rare size or lack of filters due to the size.
Whenever you plan to attach a filter keep in mind two things:
- First check if your lens has a thread on its edge to attach a filter.
- If you attach a filter, be gentle when attaching and disattaching it. Some lenses have threads more delicate than others, and if youre not gentle, you make break them. This can result in no longer being able to attach a filter and need to buy a new lens.
Finally, some lenses like the Sony 16mm Fisheye lens or the 500mm f/8 Reflex lenses have built in filters included.
Size and Weight: As part of the technical specs of any kind of gear, the size and weight is included. This can be helpful if youre looking for a light and small lens or a big and heavy one. Checking this information before purchasing (especially online) can be helpful to give you an idea of the real size and weight of the lens, since it's common in online stores to display big lenses in a small size and small lenses in a very big size or not display them at all.
Minimum aperture: Since youre more likely to use big apertures instead of small ones, those are included in the lens itself, however, the minimum aperture or big f-number is something you should also know, since it tells you just how dark the lens can be or how much Depth Of Field you can achieve with it (assuming you can have enough light for such small apertures).
Just as the maximum aperture can change if you change focal length, the same happens with the minimum aperture. In the Sony 18-20mm f/3.5-6.3, the maximum aperture at 18mm is f/22, whereas at 200mm its f/40.
In average, in the Sony Alpha lens range the maximum aperture at a lens' shortest focal length is f/22 and at the largest focal length is f/32. Keep in mind this is just an average, not the exact aperture number for each lens.
Angle of view: A very important feature of any lens, its the angle of view it possesses.
The angle of view is basically how much of the scene infront of it the lens can see. The bigger the number, the wider the angle, and the smaller the number, the tighter the angle.
Wide angle lenses have (obviously) wider angles (duh) than zoom lenses or telephotos. However, that depends on the focal length of every lens. If you got a wide angle lens like a 20mm but you also got a zoom lens that has a short focal length of 18mm, the zoom lens can see a bit more than the wide angle lens.
Zoom lenses at their biggest focal length and telephoto lenses have a small angle of view, this is because in order to compress distance and bring subjects closer, you got to sacrifice angle of view. This explains why the closer you get to something, you cant keep the surroundings inside the frame.
How much angle of view you need depends on how much of a scene you want in your picture. You may have a wide angle lens thats including too much in the picture that you dont want or a zoom lens that cant squeeze an extra person in the frame.
One thing you got to keep in mind here is that the angle of view of a full frame lens changes when you use it on a APS-C sensor camera. Remember what I said of focal length multiplier? It applies here. Since a smaller sensor crops out part of the scene that a full frame sensor could capture, this also changes the angle of view.
Example: The Sony 16mm f/2.8 Fisheye lens is designed for a full frame sensor. On a A900, that lens would have an angle of view of 180 degrees, which would make the edges of the frame take a circular shape. If you use that lens on a A700 or else, the angle is reduced to 110 degrees and you wont be able to get the fisheye view the lens is designed to give.
This is why APS-C sensors require specially made wide angle lenses and fisheye lenses. Due to the cropping the sensor does, you would need a lens like the Sony 11-18mm f/4.5-5-6 or a Sigma 10-20mm whereas in full frame a 12-24mm would work as wide angle.
Whenever you buy a lens, be sure to know the angle of view the lens has and if it will be reduced if you mount it on a APS-C sensor or smaller.
Number of aperture blades: In a lens, the more blades it has, the better picture quality since the degree of blurring it can achieve is better.
Another data thats specified in the specs its if the aperture is normal or circular. Circular aperture is better since it renders the out of focus subjects smoother than the normal aperture.
In the Sony Alpha range, the average aperture blade number is 7, and the G and Carl Zeiss lenses almost all have 9. Also worth mentioning is that almost all the lenses in the Alpha line have circular aperture, the 28mm f/2.8 is one of the exceptions.
If it has special glass elements or coatings: Usually lens makers include special lenses among the elements to correct possible light aberrations that can occur. One very common these days is the APO lens. APO is an abbreviation of apochromatic, which means it corrects the color aberrations that the other elements can cause. The APO lens element was an element used by Minolta in its range of telephoto lenses.
There are all sorts of special glass elements used by lens makers in order to correct aberrations or to further enhance the effect the lens is designed for. They usually specify them when promoting a lens.
As for coatings, whenever the lens maker doesnt specify if the lens has a special coating on the lens, it will on the specifications.
Magnification ratio: Another important value of a lens is its magnification ratio.
In simple terms, it means how much it will enlarge small things. This is something really important in macro lenses, since they are designed to enlarge things.
When you see something through a lens, its size can increase or decrease. The magnification ratio is how much that lens can bring subjects to their real size. This ratio is expressed like this: 1.0 or this 1:0.
When a lens says its magnification ratio is 1.0 it means it shows the subjects on their real size.
Magnification comes in all lenses, in some its not so visible and in others it is. However, even telephoto lenses can have a high magnification; the Tamron 70-300mm f/4-5.6 LD Di has a magnification ratio of 1:2. That means that it can make subjects appear half their real size, which effectively makes this lens into a telemacro lens: a telephoto with macro capabilities.
If it comes with any other accesories: Some lens makers supply their lenses with additional accesories such as lens hoods, carrying cases, filters, cleaning cloths, etc. It's important that you check if any accessory is supplied with every lens you purchase, otherwise you wont know if something is missing.
Questions about lenses that you have but you're afraid to ask
Does an expensive lens guarantees a good photo?
No. An expensive lens may have a lot more bells and whistles than a cheaper lens wont have, but no matter how fast, light, full of special glass, etc. the lens is, if the photographer doesnt know how to handle it or doesnt have the enough vision to create a compelling picture, not even the most expensive lenses in the world will guarantee a good picture. It all depends on the photographer and its creativity.
Is lens sharpness that important?
It's common these days for photographers to be really picky about lens sharpness. The holy grail is a lens thats sharp all around including corners and at any aperture.
The truth is, such thing hasnt existed so far, and probably will never exist.
Modern lenses are sharp enough to get good pictures, sure, some are sharper than others, but the only way in which you will scientifically measure how sharp a lens is from another is with controlled tests at a lab.
And a lab isnt the only place for photographs you can use.
Ken Rockwell points out on an article he wrote about sharpness that usually the problem is not the lens, but a bad focus, camera movement or subject movement. You can find the article here.
Sure, you dont want your pictures coming out fuzzy or not sharp enough to see the subject, but lenses these days wont fall into that unless they have a defect.
A very very very underrated lens is the Sony 28mm f/2.8. A lot of people and testers disregard this lens because its not as sharp as other more expensive wide angle lenses are.
The truth is that this lens is sharp, may not be sharp enough to cut bread, but it sure is sharp, and Ive managed to get great portraits with it indoors.
Again, its more important what you conjure up for a picture than if your lens is sharp as a shark's fang.
Is it best to go for the expensive lens instead of the cheap one?
Well, if you got money to blow, then get the expensive one, if not, the cheap one.
Price only determines three possible things in a lens: Status, quality and options.
You can buy a Sony 70-300 f/3.5-5.6 G lens and blow 800 dollars on it instead of the Sony 75-300 f/4.5-5.6 that costs 223 dollars, you will be seen as someone with serious equipment and youll have as many buttons on the lens as you do on your camera.
However, that doesnt mean that you will get great pictures with it if you dont know how to use it. You only got a long lens with lots of buttons, better glass and a lens hood that will surely scream out to everyone else: HEY, I GOT AN EXPENSIVE LENS!
To get great pictures you dont have to own the best lenses. To think that you need the best lens to get better pictures is just as stupid as to think you need an Aston Martin or a Ferrari to make it to work on time.
Its the results you create with a lens that get you awards, jobs or praise. Viewers dont think of what lenses you use when looking at your pictures. They watch the results.
A 1800 dollars lens like the Carl Zeiss 24-70mm f/2.8 T* Vario Tessar wont make you a better photographer, nor will create masterpieces nor will take pictures on its own. The only results it will get depend on what you do with it. What YOU do with it.
Expensive or cheap? Doesnt matter, its the result you get from it that counts.
Closure
This concludes our article about how to pick a lens and read their specs. I hope that now the basic terms and concepts are now clear to you and you can get a better idea of what to look for in a lens when you purchase one.
And remember, its what YOU the photographer do with a lens that matters, not the lens itself. If you ever won a prize, it certainly wouldnt go to the lens you used, would it? A lens doesnt do anything on its own afterall.
James Bond uses a Walther PPK 7.65mm gun, which is a tiny gun, and yet he always does his job. Its how you use it, not what brand or size.
Until next time.
Monday, December 8, 2008
Lenses-How To Pick One And Read Their Specs: Part 2
Basics explained
1- Why does the Sony Alpha DSLR system doesn't need stabilized lenses?
The Sony Alpha DSLRs use a different approach to stabilize an image than the one used by other camera manufacturers.
In simple terms, the Alpha use sensor stabilization, which means that when the camera senses movement, the sensor is kept as still as possible by motors inside the camera. This helps to reduce the blur seen in pictures when the camera is hand held.
The difference between this system and stabilized lenses is that all the lenses you purchase will have access to the sensor stabilization at no extra cost, making them lighter and cheaper in some cases. DSLR systems that require stabilized lenses require you to purchase each lens with stabilization or vibration reducing motors, which can make them heavier and some times more expensive.
2.- What is a bayonet mount and why Minolta and not Sony developed it?
In photography, the interface used to make a camera and a lens fit and talk to each other is called lens mount. There are screw driven mounts (like the one used in lenses you can attach to P&S cameras), friction lock and bayonet mounts.
A bayonet mount is the most used type of lens mount in DSLR cameras due to the fact that they align precisely the electronic and mechanical components of the lens. It's called bayonet because it's based on the military weapon of the same name. When soldiers needed to attach a bayonet to their rifles, they could do so quickly because of the mounting system. This also applies to photography since DSLRs allow you to change lenses much faster than a screw driven mount.
The Alpha mount was originally the Minolta AF mount, which was the first lens mount to auto focus, this mount was introduced in 1985. When Minolta had to close down operations, Sony purchased most of Minolta's assets, including lens designs, the flash mount and the lens mount. Sony rebranded the Minolta AF mount in to Alpha mount and added further improvements, such as addition of lens contacts in the mount for better camera-lens communication and the use of lenses with the flash ADI function.
All the Minolta AF lenses fit the current Alphas because they all work on the same mount. Minolta lenses older than 1985 can't be used on the Alphas unless you do some custom work on the mount to make it fit.
Lens information explained
This section will explain the items listed in the section Reading a lens of Part 1.
Maker: This states who made the lens, Sony, Minolta, Tamron, Sigma, Carl Zeiss, etc.
Focal length: A lens can zoom or not, but they all got focal length. In simple terms, focal length is how much space there is between the sensor and the lens. The less distance, means a wider angle of view, the more distance, it means the lens can reach far in the distance.
Example: The Sony 18-200mm lens tells you it has a variable focal length. It's shortest distance is 18mm and the longest end is 200mm. At 18mm the lens will have a wide angle field of view whereas at 200 it will have a very narrow view. This is an all purpose lens, which means that can be used to take portraits, landscapes or telephoto shots because of the wide distance range it covers, however this makes it bigger and heavier than other lenses, like the 18-70mm.
Example 2: The Sony 50mm is a fixed focal length lens (lenses with fixed focal lengths are called primes), this means there is 50mm between the sensor and the lens. The field of view is fixed, and to zoom or have a wider angle, you need to move back or forth physically. This focal length is often used for portraits.
Example 3: The Sony 11-18mm is a super wide angle lens with a zoom range. The widest distance is 11mm and the longest distance it will go is 18mm. This lens is designed to take wide angle shots but you can zoom in or out to allow more or less of the scene to be captured. It can't take shots farther than 18mm because it's not designed for that.
Example 4: The Sony 500mm lens is a super telephoto prime lens. You can't move its focal length and everything you will see with this lens will be at 500mm, which will make far things really close to the view. You cant shoot nearby subjects unless they are within the focusing distance of this lens.
Example 5: The Sony 18-70mm is a zoom lens, usually sold as part of a kit. It has a wide angle distance of 18mm and a telephoto distance of 70mm. This lens doesn't have a long reach like the Sony 18-200 or 18-250. It is designed as an all purpose lens which covers enough distance for portraits or landscapes without being too heavy. Since it's usually the first lens most Alpha users get, it teaches them how to pick what focal length to shoot at. Eventually the user will need more or less focal length for different shots and that's when they move to other kind of lenses with different focal lengths.
So when you see a lens with 1 focal length number on it, it means its a prime lens and the zoom changes as you move, if you see a lens with 2 focal length numbers on it, it displays how short and far it will go.
Maximum constant aperture or variable depending on focal length: A lens can or can not keep a constant aperture at a given focal length. It depends on it's construction, lenses that can keep a constant aperture are usually a lot bigger and heavier than one that has a variable aperture.
But what does this mean?
All lenses have a maximum aperture number, such as 1.4, 2.8, 3.5, 4, 8, etc. Having a big aperture increases the amount of light that reaches the sensor and reduces depth of field (how much of the subject is in focus). Depending on the lens construction, the lens can hold on to the maximum aperture even if you zoom or not.
Example: The Sony 70-200 f/2.8 lens its a telephoto lens that can keep the aperture at 2.8 in all the focal length range, be it 70, 100, 150, or 200mm. This is really helpful because if you're shooting under low light and you need to zoom and keep the f number at 2.8, the lens will be able to keep it, giving you the necessary light to work with. The downside of this lens is that is bigger and heavier than other telephoto lenses.
Example 2: The Sony 75-300mm f/4.5-5.6 its another telephoto lens, but this one has a variable aperture. At 75mm, the lens biggest aperture will be f/4.5, but if you zoom at 300mm, the lens' maximum aperture changes to f/5.6. Why does it happen? The lens construction doesn't allow the lens to keep the aperture constant, therefore it has to change when the focal length changes. The plus point of this is that lens size is not too big and heavy, but you have to sacrifice light if you zoom in.
Example 3: The Sony 18-250mm f/3.5-6.3 its a zoom lens with variable aperture. At 18mm the maximum aperture will be f/3.5 and at 250mm it will be f/6.3. As you move from 18 to 250mm, the aperture will change to f/4, 4.5, 5.6 depending on the focal length until you reach f/6.3 at 250mm.
So when you see a lens with just one f-number, it means its aperture it's constant at any focal length (if its a zoom/telephoto lens), when you see a lens with 2 f-numbers, the first means the maximum aperture for the shortest focal length, and the second means the maximum aperture at the longest focal length.
If your photography requires you to work with low light most of the time, a lens with a constant aperture may be better for you than a variable one. The downside of these lenses are their size, weight and price. They tend to be big, heavy and expensive. Third party lens makers however also offer constant aperture lenses at more affordable prices and lighter too.
On the other hand, if what you need are lenses you can carry around, a variable aperture lens is the way to go. You will need to play with shutter speed and ISO to keep the exposure as needed to compensate for aperture changes with focal length.
Focusing motors: Higher grade lenses have focusing motors built into them, unlike normal lenses that depend on the camera's focusing motor located at the mount.
The advantage of these motors is that they make focusing a lot faster and silent.
These motors have all sorts of names depending on the lens maker. In the Sony/Minolta lens range this motor is called SSM which stands for Super Sonic Motor. This motor works at ultrasonic vibrations and makes focusing a lot more precise.
Example: The Sony 70-300 f/4.5-5-6 G SSM is a lens that carries this motor.
Usually this motor is found in high grade lenses, which makes the lens expensive.
Third party lens makers also use this kind of ultra sonic motors, but name them differently. An example is Sigma's H(yper)S(onic)M(otor). Carl Zeiss also uses the SSM motor in their lenses for the Alpha mount.
Higher grade lenses: In the Alpha system, there are lenses that have better quality over the rest of the lenses that are compatible with this mount. By better quality I mean better glass that reduces chromatic aberrations, distortion, have SSM, have more options to customize the lens (like a focus holder button or focus range limiter). Minolta used the G letter to identify these lenses from the rest, and Sony kept it.
Whenever you see a Sony/Minolta lens with a G on it like the Sony 70-300 f/4.5-5-6 G SSM, it means its the best quality you can find in a lens made by Sony/Minolta.
There are also lenses made by Carl Zeiss. These lenses are also high grade lenses, the build quality, glass and coatings used are of top quality as well. They also use SSM.
All Carl Zeiss lenses for the Alpha mount have the ZA designation in the body. Ziess makes lenses for other camera manufacturers as well, but the ones for the Alpha mount are labeled as ZA. The most demanded lens from Zeiss is the Vario Sonnar T* 24-70mm SSM f/2.8 ZA.
That is a zoom lens with a 24-70mm focal range and constant f/2.8 aperture. Uses SSM and has digital coatings (T* designation), the Vario Sonnar designation means its a big lens and the ZA means its a Zeiss lens made for the Alpha mount.
The Carl Zeiss lenses and the G series lenses are the top of the line for the Alpha DSLR system.
Lenses designed for APS-C sensors: Due to the difference in size sensors, image cropping, focal length multiplier issues, etc. manufacturers faced the need to develop lenses that covered the APS-C sized sensor in order to create the desired effect the lens should create, such as wide angle view or effective zoom range for that sensor. A 20mm wide angle lens for full frame is 30mm in APS-C, and the wide angle effect is not visible as it should be.
These specially APS-C size lenses carry the DT designation in order to prevent them from being confused with full frame lenses.
DT stands for Digital Technology. Even though full frame sensors are now available for DSLRs, in the beginning of the digital age, most DSLR makers used the APS-C size and it became a standard size. All lenses that carry the DT designation are only to be used in APS-C sensors. You can use them in full frame, but vignetting will be created.
Lenses like the DT 11-18mm f/4.5-5.6, DT 18-70mm f//3.5-5.6, DT 18-200mm f/3.5-6.3, and the Vario-Sonnar T* DT 16-80mm f/3.5-4.5 ZA are all made specifically for APS-C sensors.
Tamron designates its APS-C size lenses as Di-II, Sigma labels them as DC. Carl Zeiss also uses the DT denomination.
If you need a wide angle lens or a fisheye lens and you use a camera with an APS-C sensor, make sure you look for the DT designation in Sony lenses or the equivalent for third party makers in order to get the effective focal length you need, otherwise you will end up with a different focal length due to cropping.
Type of coatings: A lens focuses light rays in a single point, making it a filter between light and the sensor.
When light hits a lens, it creates all sorts of aberrations, such as chromatic (when subjects have colors they don't have in reality), flare (when light is diffused across the lens surface and make streaks of light appear all over the photo) or ghosting (when a virtual image is formed separate or overlapping the real subject), etc.
In order to address these issues, coatings are applied to lenses. If you grab a lens and look at the front element, you will see there are colors on it, those are the coatings.
Some makers like to label the lens to display the type of coating used on it. Zeiss for example marks their lenses with a T* denomination. There are a lot of denominations for digital coatings and they vary from maker to maker.
The coatings also protect the front lens element, since its the piece of glass exposed to the environment.
The quality of coatings or amount of them used on a lens varies depending on the quality of the lens. Usually higher grade lenses have better coatings than the normal lenses.
Lens kind denomination: Usually a lens doesn't mark if its a telephoto, wide angle, zoom, etc. But sometimes lens makers do mark the lens with the kind it is.
Examples like the 50mm f/2.8 Macro, 135mm f/2.8 Smooth Transition Focus (STF), 500mm f/8 Reflex are example of lenses that carry their kind printed into them. This works to distinguish them from other lenses with similar focal lengths. This way you wont confuse the 50mm f/2.8 Macro with the 50mm f/1.4.
In the case of the 500mm f/8 Reflex, the marking is necessary for two reasons: this lens is not made like all the lenses are, this uses a mirror as part of its elements, which makes it a kind of small telescope and it creates a donut shape of the stuff not in focus, second is because there are other 500mm lenses available, but not constructed like this one, so the marking Reflex helps to differentiate this one from other lenses with 500mm focal lengths.
It's worth mentioning that the Sony/Minolta 500mm f/8 Reflex is the first and only reflex lens to autofocus in the world.
Brief term glossary
SSM: SuperSonicMotor, focusing ultra sonic motor found in G and ZA series lenses.
G: G lens Series, professional high grade lenses.
DT: Digital Technology, denomination to indicate lenses designed especifically for APS-C sensors.
ZA: Zeiss Alpha, Carl Zeiss lenses made for the Alpha mount.
End of Part 2.
1- Why does the Sony Alpha DSLR system doesn't need stabilized lenses?
The Sony Alpha DSLRs use a different approach to stabilize an image than the one used by other camera manufacturers.
In simple terms, the Alpha use sensor stabilization, which means that when the camera senses movement, the sensor is kept as still as possible by motors inside the camera. This helps to reduce the blur seen in pictures when the camera is hand held.
The difference between this system and stabilized lenses is that all the lenses you purchase will have access to the sensor stabilization at no extra cost, making them lighter and cheaper in some cases. DSLR systems that require stabilized lenses require you to purchase each lens with stabilization or vibration reducing motors, which can make them heavier and some times more expensive.
2.- What is a bayonet mount and why Minolta and not Sony developed it?
In photography, the interface used to make a camera and a lens fit and talk to each other is called lens mount. There are screw driven mounts (like the one used in lenses you can attach to P&S cameras), friction lock and bayonet mounts.
A bayonet mount is the most used type of lens mount in DSLR cameras due to the fact that they align precisely the electronic and mechanical components of the lens. It's called bayonet because it's based on the military weapon of the same name. When soldiers needed to attach a bayonet to their rifles, they could do so quickly because of the mounting system. This also applies to photography since DSLRs allow you to change lenses much faster than a screw driven mount.
The Alpha mount was originally the Minolta AF mount, which was the first lens mount to auto focus, this mount was introduced in 1985. When Minolta had to close down operations, Sony purchased most of Minolta's assets, including lens designs, the flash mount and the lens mount. Sony rebranded the Minolta AF mount in to Alpha mount and added further improvements, such as addition of lens contacts in the mount for better camera-lens communication and the use of lenses with the flash ADI function.
All the Minolta AF lenses fit the current Alphas because they all work on the same mount. Minolta lenses older than 1985 can't be used on the Alphas unless you do some custom work on the mount to make it fit.
Lens information explained
This section will explain the items listed in the section Reading a lens of Part 1.
Maker: This states who made the lens, Sony, Minolta, Tamron, Sigma, Carl Zeiss, etc.
Focal length: A lens can zoom or not, but they all got focal length. In simple terms, focal length is how much space there is between the sensor and the lens. The less distance, means a wider angle of view, the more distance, it means the lens can reach far in the distance.
Example: The Sony 18-200mm lens tells you it has a variable focal length. It's shortest distance is 18mm and the longest end is 200mm. At 18mm the lens will have a wide angle field of view whereas at 200 it will have a very narrow view. This is an all purpose lens, which means that can be used to take portraits, landscapes or telephoto shots because of the wide distance range it covers, however this makes it bigger and heavier than other lenses, like the 18-70mm.
Example 2: The Sony 50mm is a fixed focal length lens (lenses with fixed focal lengths are called primes), this means there is 50mm between the sensor and the lens. The field of view is fixed, and to zoom or have a wider angle, you need to move back or forth physically. This focal length is often used for portraits.
Example 3: The Sony 11-18mm is a super wide angle lens with a zoom range. The widest distance is 11mm and the longest distance it will go is 18mm. This lens is designed to take wide angle shots but you can zoom in or out to allow more or less of the scene to be captured. It can't take shots farther than 18mm because it's not designed for that.
Example 4: The Sony 500mm lens is a super telephoto prime lens. You can't move its focal length and everything you will see with this lens will be at 500mm, which will make far things really close to the view. You cant shoot nearby subjects unless they are within the focusing distance of this lens.
Example 5: The Sony 18-70mm is a zoom lens, usually sold as part of a kit. It has a wide angle distance of 18mm and a telephoto distance of 70mm. This lens doesn't have a long reach like the Sony 18-200 or 18-250. It is designed as an all purpose lens which covers enough distance for portraits or landscapes without being too heavy. Since it's usually the first lens most Alpha users get, it teaches them how to pick what focal length to shoot at. Eventually the user will need more or less focal length for different shots and that's when they move to other kind of lenses with different focal lengths.
So when you see a lens with 1 focal length number on it, it means its a prime lens and the zoom changes as you move, if you see a lens with 2 focal length numbers on it, it displays how short and far it will go.
Maximum constant aperture or variable depending on focal length: A lens can or can not keep a constant aperture at a given focal length. It depends on it's construction, lenses that can keep a constant aperture are usually a lot bigger and heavier than one that has a variable aperture.
But what does this mean?
All lenses have a maximum aperture number, such as 1.4, 2.8, 3.5, 4, 8, etc. Having a big aperture increases the amount of light that reaches the sensor and reduces depth of field (how much of the subject is in focus). Depending on the lens construction, the lens can hold on to the maximum aperture even if you zoom or not.
Example: The Sony 70-200 f/2.8 lens its a telephoto lens that can keep the aperture at 2.8 in all the focal length range, be it 70, 100, 150, or 200mm. This is really helpful because if you're shooting under low light and you need to zoom and keep the f number at 2.8, the lens will be able to keep it, giving you the necessary light to work with. The downside of this lens is that is bigger and heavier than other telephoto lenses.
Example 2: The Sony 75-300mm f/4.5-5.6 its another telephoto lens, but this one has a variable aperture. At 75mm, the lens biggest aperture will be f/4.5, but if you zoom at 300mm, the lens' maximum aperture changes to f/5.6. Why does it happen? The lens construction doesn't allow the lens to keep the aperture constant, therefore it has to change when the focal length changes. The plus point of this is that lens size is not too big and heavy, but you have to sacrifice light if you zoom in.
Example 3: The Sony 18-250mm f/3.5-6.3 its a zoom lens with variable aperture. At 18mm the maximum aperture will be f/3.5 and at 250mm it will be f/6.3. As you move from 18 to 250mm, the aperture will change to f/4, 4.5, 5.6 depending on the focal length until you reach f/6.3 at 250mm.
So when you see a lens with just one f-number, it means its aperture it's constant at any focal length (if its a zoom/telephoto lens), when you see a lens with 2 f-numbers, the first means the maximum aperture for the shortest focal length, and the second means the maximum aperture at the longest focal length.
If your photography requires you to work with low light most of the time, a lens with a constant aperture may be better for you than a variable one. The downside of these lenses are their size, weight and price. They tend to be big, heavy and expensive. Third party lens makers however also offer constant aperture lenses at more affordable prices and lighter too.
On the other hand, if what you need are lenses you can carry around, a variable aperture lens is the way to go. You will need to play with shutter speed and ISO to keep the exposure as needed to compensate for aperture changes with focal length.
Focusing motors: Higher grade lenses have focusing motors built into them, unlike normal lenses that depend on the camera's focusing motor located at the mount.
The advantage of these motors is that they make focusing a lot faster and silent.
These motors have all sorts of names depending on the lens maker. In the Sony/Minolta lens range this motor is called SSM which stands for Super Sonic Motor. This motor works at ultrasonic vibrations and makes focusing a lot more precise.
Example: The Sony 70-300 f/4.5-5-6 G SSM is a lens that carries this motor.
Usually this motor is found in high grade lenses, which makes the lens expensive.
Third party lens makers also use this kind of ultra sonic motors, but name them differently. An example is Sigma's H(yper)S(onic)M(otor). Carl Zeiss also uses the SSM motor in their lenses for the Alpha mount.
Higher grade lenses: In the Alpha system, there are lenses that have better quality over the rest of the lenses that are compatible with this mount. By better quality I mean better glass that reduces chromatic aberrations, distortion, have SSM, have more options to customize the lens (like a focus holder button or focus range limiter). Minolta used the G letter to identify these lenses from the rest, and Sony kept it.
Whenever you see a Sony/Minolta lens with a G on it like the Sony 70-300 f/4.5-5-6 G SSM, it means its the best quality you can find in a lens made by Sony/Minolta.
There are also lenses made by Carl Zeiss. These lenses are also high grade lenses, the build quality, glass and coatings used are of top quality as well. They also use SSM.
All Carl Zeiss lenses for the Alpha mount have the ZA designation in the body. Ziess makes lenses for other camera manufacturers as well, but the ones for the Alpha mount are labeled as ZA. The most demanded lens from Zeiss is the Vario Sonnar T* 24-70mm SSM f/2.8 ZA.
That is a zoom lens with a 24-70mm focal range and constant f/2.8 aperture. Uses SSM and has digital coatings (T* designation), the Vario Sonnar designation means its a big lens and the ZA means its a Zeiss lens made for the Alpha mount.
The Carl Zeiss lenses and the G series lenses are the top of the line for the Alpha DSLR system.
Lenses designed for APS-C sensors: Due to the difference in size sensors, image cropping, focal length multiplier issues, etc. manufacturers faced the need to develop lenses that covered the APS-C sized sensor in order to create the desired effect the lens should create, such as wide angle view or effective zoom range for that sensor. A 20mm wide angle lens for full frame is 30mm in APS-C, and the wide angle effect is not visible as it should be.
These specially APS-C size lenses carry the DT designation in order to prevent them from being confused with full frame lenses.
DT stands for Digital Technology. Even though full frame sensors are now available for DSLRs, in the beginning of the digital age, most DSLR makers used the APS-C size and it became a standard size. All lenses that carry the DT designation are only to be used in APS-C sensors. You can use them in full frame, but vignetting will be created.
Lenses like the DT 11-18mm f/4.5-5.6, DT 18-70mm f//3.5-5.6, DT 18-200mm f/3.5-6.3, and the Vario-Sonnar T* DT 16-80mm f/3.5-4.5 ZA are all made specifically for APS-C sensors.
Tamron designates its APS-C size lenses as Di-II, Sigma labels them as DC. Carl Zeiss also uses the DT denomination.
If you need a wide angle lens or a fisheye lens and you use a camera with an APS-C sensor, make sure you look for the DT designation in Sony lenses or the equivalent for third party makers in order to get the effective focal length you need, otherwise you will end up with a different focal length due to cropping.
Type of coatings: A lens focuses light rays in a single point, making it a filter between light and the sensor.
When light hits a lens, it creates all sorts of aberrations, such as chromatic (when subjects have colors they don't have in reality), flare (when light is diffused across the lens surface and make streaks of light appear all over the photo) or ghosting (when a virtual image is formed separate or overlapping the real subject), etc.
In order to address these issues, coatings are applied to lenses. If you grab a lens and look at the front element, you will see there are colors on it, those are the coatings.
Some makers like to label the lens to display the type of coating used on it. Zeiss for example marks their lenses with a T* denomination. There are a lot of denominations for digital coatings and they vary from maker to maker.
The coatings also protect the front lens element, since its the piece of glass exposed to the environment.
The quality of coatings or amount of them used on a lens varies depending on the quality of the lens. Usually higher grade lenses have better coatings than the normal lenses.
Lens kind denomination: Usually a lens doesn't mark if its a telephoto, wide angle, zoom, etc. But sometimes lens makers do mark the lens with the kind it is.
Examples like the 50mm f/2.8 Macro, 135mm f/2.8 Smooth Transition Focus (STF), 500mm f/8 Reflex are example of lenses that carry their kind printed into them. This works to distinguish them from other lenses with similar focal lengths. This way you wont confuse the 50mm f/2.8 Macro with the 50mm f/1.4.
In the case of the 500mm f/8 Reflex, the marking is necessary for two reasons: this lens is not made like all the lenses are, this uses a mirror as part of its elements, which makes it a kind of small telescope and it creates a donut shape of the stuff not in focus, second is because there are other 500mm lenses available, but not constructed like this one, so the marking Reflex helps to differentiate this one from other lenses with 500mm focal lengths.
It's worth mentioning that the Sony/Minolta 500mm f/8 Reflex is the first and only reflex lens to autofocus in the world.
Brief term glossary
SSM: SuperSonicMotor, focusing ultra sonic motor found in G and ZA series lenses.
G: G lens Series, professional high grade lenses.
DT: Digital Technology, denomination to indicate lenses designed especifically for APS-C sensors.
ZA: Zeiss Alpha, Carl Zeiss lenses made for the Alpha mount.
End of Part 2.
Thursday, December 4, 2008
Lenses-How To Pick One And Read Their Specs: Part 1
Have you ever tried to purchase a lens but you had NO idea what to keep in mind or what to look for in it?
Maybe the store's salesperson tried to sell you the lens he/she wanted you to buy, showing you the numbers in front of the lens or the specs, but youre not sure that is the lens you need/want.
Have you ever researched for a lens and the full name of it was: Lensmaker 10-300mm f 2.8-8 Macro G APO DT SSM and you didnt understand what those things mean?
Well fear no more, this series of articles is going to give you a bearing of what all those things in a lens mean and what you should keep in mind when purchasing one.
The basics
There a few things you need to know before we begin:
Maybe the store's salesperson tried to sell you the lens he/she wanted you to buy, showing you the numbers in front of the lens or the specs, but youre not sure that is the lens you need/want.
Have you ever researched for a lens and the full name of it was: Lensmaker 10-300mm f 2.8-8 Macro G APO DT SSM and you didnt understand what those things mean?
Well fear no more, this series of articles is going to give you a bearing of what all those things in a lens mean and what you should keep in mind when purchasing one.
The basics
There a few things you need to know before we begin:
- The Sony Alpha DSLR system doesnt require stabilized lenses like other systems.
- The Sony Alpha DSLR system uses a bayonet mount called Alpha mount which was inherited from Minolta.
- The official lens maker for the Alpha DSLR system is Sony. Minolta AF lenses are also compatible and are considered official since the mount was originally developed by Minolta.
- There are third party lens makers who make compatible Alpha mount lenses, such as Tamron, Sigma or Carl Zeiss, etc.
- Lenses made for Minolta SLRs are full frame lenses (35mm film), they can be used with the Sony Alpha DSLRs as long as they are A(uto)F(ocus). Lenses made by Sony or other maker are full frame lenses unless specified different.
- In the Alpha DSLR system, there are two sensor sizes: APS-C (23.6 x 15.7mm) and Full Frame (36 x 24mm), Full frame lenses can be used with Alpha DSLRs equipped with APS-C sized sensors, APS-C lenses can be used with full frame Alpha DSLRs but they cause vignetting or a darkening around the image. The vignetting occurs because APS-C lenses dont have the same field of view that Full Frame lenses do, resulting in cropping. Using these lenses on a full frame DSLR is possible but not recommended.
- In the Alpha DSLR line the following cameras use APS-C sized sensors: A100/200/300/350/700. Cameras that use full frame sensors: A900.
Type of lenses
The first thing you need to determine when you look for a lens is what do you need it to do.
Do you need it for really close up shots? You want a lens that will let you include everyone when taking group pictures? You need a lens to get far into the scene without you moving?
There are 5 types of lenses:
- Macro lenses, for close ups of really small things.
- Wide angle lenses (and Super wide angle), they have a wider field of view so you can include more of the scene in the picture.
- Zoom lenses, lenses with variable focal lengths that can let you take wide angle shots or really close pictures and anything in between.
- Telephoto (and Super telephoto) lenses, these lenses are larger than Zoom lenses, they allow you to reach even farther without you physically moving.
- Special effect lenses, These allow you to create inusual effects into your pictures that other lenses normally cant do, such as defocusing most of the image, altering the perspective, etc.
The macro, wide angle, telephoto and special effect lenses can have a zoom range in which you can move closer or away from your subject by moving a zoom ring in your lens but they can also be of fixed focal length, this means you cant move closer or away from your subject by moving a zoom ring in your lens, you got to physically move.
Reading a lens
Most lenses display their main specifications on the front, but not all of them, some don't due to their design or style.
The way the information is displayed also varies, Sony displays the information differently from Carl Zeiss on their lenses.
The information that lenses display on them is:
- Maker
- Focal length
- Maximum constant aperture or variable depending on focal length
- If it has a focusing engine built in
- If its a higher grade lens (meaning better type of glass used and better image quality overall)
- If its meant to be used specifically with APS-C sensors
- Type of coatings used on the glass
- If its a Macro, Reflex, Smooth Transition Focus lens etc.
Technical data not displayed in a lens
The lenses also have technical information that you should also keep in mind when purchasing it, this information is:
- Lens groups/elements
- Minimum focus distance
- Filter diameter
- Size
- Weight
- Minimum aperture
- Angle of view
- Number of aperture blades
- If it has special glass elements or coatings
- Magnification ratio
- If it comes with any other accesories
Focal length multiplier
An important thing to keep in mind when purchasing a lens is the size of your sensor.
As mentioned above, the Alpha DSLR cameras use APS-C and Full frame sized sensors.
If you use a camera with an APS-C sensor, the effective focal length of your lens is modified because the APS-C sensor is smaller than the Full frame sensor.
This difference is called focal length multiplier.
What is this? In simple terms its how many times the length of the lens is multiplied taking in account the size of the sensor.
APS-C sensors are 1.5 times smaller than a full frame sensor, this means that the field of view of this sensor is reduced, and parts of the image that a full frame sensor can see, the APS-C sensor cant.
This translates that if you buy a 50mm lens, in an APS-C sensor the effective distance will be 75mm. 50 x 1.5 = 75
With telephoto lenses this is an advantage since you can get to the same place in less focal length than a full frame camera. If you use an APS-C sensor, you will get at 300 mm whereas a full frame camera needs 450 mm.
The downside is that wide angle lenses have to be designed especially for the APS-C sensor size, since full frame wide angle lenses dont yield the wider field of view on the smaller sensor. This translates in lenses with really short focal lengths (10-20mm for APS-C against 12-24mm for full frame) The problem is that they are expensive due to the complexity of their construction.
Sensor sizes:
Focal length multiplier:
Red for full frame, blue for APS-C
Images obtained from Wikipedia
In the following parts, the items listed above will be explained.
End of Part 1.
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