Naming of the lenses is as follows: “Canon EF 70-200mm f2.8L IS”
Which translates into: EF (mount) 70-200mm (zoom) f/2.8(apperture)L (series) IS (image stabilization)
Mount. Canon has two types of semi-compatible mounts EF and EF-S:
- EF mount is compatible with 35mm (aka full-frame) chips and film cameras. All of Canon cameras can be paired up with this lense.
- EF-S mount is a digital-only mount, and EF-S lenses can be only mounted on Rebels and 30D-like cameras, but not the film cameras or top of the line full-frame cameras. This has to do with the fact that digital chips (due to the their cost of production) are smaller than 35 mm film frames, this is why on a film camera, human eye equivalent is 75-80mm focal length, while on digitals, it’s 50mm. If one were to actually mount an EF-S lense on 35mm equivalent camera and take a picture, the picture would be cropped from all sides. Here is a link to explanation of the chip size. Here is a good write-up by a real pro. The top of the line 1D and 5D cameras cannot use EF-S lenses because their chips are bigger.
Zoom. Zoom numbers tell you what range it covers. For a typical DSLR (with a APS-C sized chip):
- < 40mm – wide angle and super wide angle – the picture include “more” than your eye sees from the same position. The objects will appear smaller.
- 40 – 70mm – “normal” lens – roughly equals to the focal range of human eye, you’ll see subjects 1:1
- > 70mm – tele lens. the resulting image will be “zoomed in” with details standing out
To estimate the equivalent of the classification above for the full-frame, multiply the numbers by factor of 1.6. For larger medium (medium format cameras, for example). Here is more info.
If there is only one number, the lens you are looking at is a prime lens. More about them below.
IS – Image Stabilization system (Nikon’s equivalent is VR). IS is a special gyroscope system that attempts to compensate for small movement of the camera when shooting in low conditions, this allows taking sharper images. Here is more information.
L Series – L is the designation for pro-level lenses from Canon. These lenses have the the best optics there is, pass the most light (so you can shoot in darker conditions), and are weather/dust proof. Generally they cost a lot and can be identified by their white color (great marketing trick – look at any sport events- all you see is white lenses on the sides, where photographers are), and a red line on the barrel. Really high quality lenses, but probably not worth starting with. Careful while browsing on the website, as just looking at them makes your wallet feel lighter.
Prime vs Zoom. Prime lens has only one focal length, which means that it doesn’t “zoom” and the only zoom that is available is “zooming with your own feet” (get closer or farther from the subject to zoom in or out). A logical thought at this point would be “well, gee, if you have zoom lenses, why would anybody need a prime lens?” The answer is: zoom lenses due to complexity of construction do not pass as much light as primes do. And light, my dear friends, for a photographer is everything! So, it’s a trade-off of flexibility vs sharpness and ability to shoot in darker conditions. I would LOVE to have a set of prime lenses for all possible situations, but it’s impractical. It would be expensive, impractical for action shots, and would require a huge camera bag. There are good zoom lenses, such as 28-135 IS that are well built, and cover good amount of focal length for most of the applications. There are many discussions what lens set would make a good starter kit. Here, here, and here are some examples.
One lens that is worth mentioning separately is the Canon EF 50mm f/1.8 lens. This is the best value in the canon lens lineup. Sure, it’s a plastic body (as opposed to metal), and it’s not as durable, but the pictures I LOVE to use it for portraits, as 1.8 aperture will create a beautiful blur.
Auto Focus vs Manual Focus. Most of the modern lenses (tilt-shifts and other exotic animals aside) have auto focus, so it’s not a question of whether or not to buy one with it. Whether or not you choose to use it is a different story. I rely on auto focus 75% of the time, and pay the price every once in a while. In 25% cases (primarily in portraits) I switch to manual. I have a friend who uses manual focus most of the time, so every time he returns my lens (or I borrow his) I have to check the auto focus switch.