Photography-A Science Of Trade-Offs

Preface.

Whether youre a rookie, an amateur or a seasoned pro, you will come across something that sooner or later manifests in photography, actually, its sooner and frequently rather than later and rarely.

And that is the fact that photography is full of TRADE OFFS.

To pick or not to pick.

By trade off is meant when you pick a choice that requires you to compromise or sacrifice another one.

An example of this would be when you are given a choice between having water or juice. If you pick water, you will get a healthy drink that will benefit your health, but that wont have a taste at all, whereas if you pick a juice, you will get a drink that will taste good and may be healthy as well, but may add carbohydrates to your body that water doesnt.

Getting the point now?

Well, photography is full of this kind of decisions, and either you learn to live with it and do the best you can with the trade offs or you will have a hard time taking pictures.

Let's look at an example of a trade off in photography:

Youre out in the street after sunset, and you want to take a picture of the people walking around in the park that youre at as well, you take a shot with a fast shutter speed and small aperture, this in order to freeze motion and achieve a good depth of field.

But when you review your shot, its really dark, almost black, and the only visible speckles of light you can see are the lamps around the park.

You go to the other extreme, you open your lens as much as possible and reduce the shutter speed as well, you take your shot, but you come up with a shot with little in focus, blurry and possible overexposed.

Has it ever happened to you? It happens to all of us as we learn to use our camera and photography.

The choice is yours.

In the above example in order to achieve a shot with frozen movement, you would have needed to pick a fast shutter speed and: a) big aperture or b) high ISO (and in some cases: c) both).

Unfortunately in photography you cant have it all.

From the very start in photography youre confronted with trades offs. When you first start looking for a camera, you will find millions of options, styles, brands, etc.

Even if you are loyal to one brand in particular, you will still have a lot of choices.

And the trade offs appear: Should I buy the one that I can carry in my pocket or the DSLR? Should I go for the one with 10 megapixels or the one with 24 megapixels?

If you pick, lets say, a DSLR, you need lenses for it, a 18-70mm? a 18-250mm? a 70-300mm? a 10-20mm? a Carl Zeiss 24-70mm? a Sony G Series 70-400?

All of them have their pros and cons, and by purchasing one in particular, you gain options and you let go others that other lens has.

If you buy a Sony 11-18mm lens against a 18-250mm, you will have gained wide angle view but have let go of zoom and telephoto capabilites.

If you buy a Carl Zeiss 24-70mm instead of a Sony G Series 70-300mm, you will have gained the best glass available for the Alpha DSLR line, but wont have the reach the other one has (The G series is also a great quality lens in the Alpha DSLR line) .

One reason why lenses like the 18-200mm, 18-250mm, 55-200mm and such are popular amongst photographers is because they provide a wide range of distance they can cover without changing lenses. They provide a good wide angle vision and good telephoto range, but if you need a wider angle or to reach farther in the distance, you will need to change lenses.

Once you get over that, you're just about to begin dealing with trade offs.

Field decisions

Once you picked what camera and lens to use, you will have to work around trade offs as you go along or use them to your advantage.

If you want shallow depth of field, you got to sacrifice focus in most of the picture. If you want a fast shutter speed and there is not enough light, you will have to open up the aperture or increase the ISO, which will in turn, ask you to sacrifice focus or add noise to your picture.

Another issue you can come across, is whether or nor shoot RAW or JPEG. Shooting JPEG gives you more time to do more shooting as the camera gives you the processed file already and it doesnt take up as much space as RAW does, but you have to accept the compression the file requires and if you edit it, accept the fact that the file will lose quality each time you alter it (thats why its better to make a copy from the original file and work with the copy), whereas shooting RAW gives you access to the complete resolution your camera can offer with no compression (unless you shoot cRAW in the A700/900) but will take up more space in your memory card and will require you to sit down in the computer and do adjustments the camera can make on its own like setting White Balance, color tone and such. Depending on how experienced you are, this may be a big time consuming process.

You will be out in the field (and by field I mean forest, street, studio or wherever you do your photography) and face lots of questions you need to solve FAST in order to use your time as best as possible; should you use flash instead of natural light with the model? Should you wait for tomorrow to get the light you want or will you work and make something creative with the current light? Would it be better to use a fast lens in order to get a faster shutter speed so you wont need too much time to take a picture? Do you need to change lens in order to reach that bird standing on the tree far away? Should you tell the kid to stay still or let him run around to get the picture? Should you shoot in black and white or color or sepia? Would the picture look better if you use a color filter?

The whole point and closure

The whole point of this is to show you that in photography there are thousands of options to pick from or work with but you got to keep in mind that for every choice you take, you need to let something go, but that doesnt necessarily mean that you let go of a good picture.

The faster you learn to make up your mind about trade offs, the more pictures you will get. Your working method may be quick or slow, but if you manage to decide quickly about whether you should shoot at f/2.8 or f/8.0 in order to get good depth of field, the less likely you will miss a shot since you will be ready and your time will be maximized to get as much shots as possible. If you take too long deciding what would be better, the less shots you take, you may miss an oportunity youll never get again and the less you will get done.

The real photographer is the one that works around trade offs fast and gets the shot he/she wants or as close as possible OR uses the trade offs to his/her advantage in order to make a unique looking shot, even if it wasn't the one that was originally intended, the bad photographer is the one who blames its camera the fact the shot didnt come out the way they wanted to but they didnt pay attention to the camera settings, their subject or the light available and dont know photography well enough to know about the fact that if you select a shutter speed of 1/4000 at a dusk, you will need a large aperture or a real high ISO to get a properly exposed shot.

You can't have it all every time, but that doesnt mean you cant have as much as possible.

Finally, there is one fact to observe here. There are a lot of people who think that the only way to get good photos is by having good equipment, however, they dont bother to learn about light management or how to use their camera and think that by having X brand will solve all their problems. They get a X brand camera and their pictures still blow, so they think they need F brand, they get an F brand camera and their pictures still blow, so they think they need K brand, notice a pattern here?

These are the people who think that the camera knows what they are thinking so they expect it to get the shot they are thinking. These are the people who think that the sensor can see as our eyes do and when the shot doesnt come out as they wanted, they think brand Q sucks and they need another one.

These people never before have heard about trade offs because to them a camera must be able to do what they want it to do. So if the picture isnt sharp enough to them, they think they need to upgrade to a 10,000 dollar lens in order to get sharp pictures or get a $8,000 camera. They never bother to check if the lens its open at f/1.4.

A trade off is a trade off, no matter if youre on a $400 body or a $100,000 one. You can do great things with a cheap camera or have the best camera available but do mediocre shots.

The trick is to learn to manage them quickly and know that you will have to deal with them at some point.

Trade offs begin when you turn on the camera, you could avoid the hassle and not turn it on, but whats the fun in having everything simple all the time?

Trade offs, deal with them and use them to your advantage or pick another hobby/career.

And that itself, it's a trade off.

Visual Guide To Change Focusing Screens On A900

One great feature of the A900 is that you can change the focusing screen without having to send your camera to an authorized repair center.

If you own an A900, this video guides you step by step on how to change the focusing screen yourself.

The focusing screen is that piece of glass that goes over the mirror that has the lines you end up seeing in the viewfinder. It can be changed to one that has a grid and the points of composition in compliance with the rule of thirds, or a plain but bright one for manual focusing.

You can find the Focusing Screen Type L and the Focusing Screen Type M in SonyStyle.

Bear in mind that the A900 is the only Alpha DSLR that allows the owner to change the focusing screens, the rest of the Alphas can have the screen changed, but only by authorized personnel, otherwise it may void your warranty.

If you attempt this kind of procedure, I suggest you watch the video a few times before proceeding. Get a good idea of what you need to do, practicing the movements first is also recommended.

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:

1. First check if your lens has a thread on its edge to attach a filter.
2. 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.

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.

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:

• 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.