The lens… probably one of the most important pieces of equipment a photographer carries. Each serves it’s own function. Failure to use the right lens may cause the artistic vision and technical execution of the setting to not turn out.  Lenses are EXPENSIVE so read on before you click buy!

There are so many words and definitions that go with lenses that it can be confusing… and they are SO expensive to buy. Here is a definition of the major lens terminology, defined in plain English.

All about focal length: (multiply the MM number by 1.5 for Nikon crop sensor cameras and 1.6 for Canons)

• A Wide Angle Lens is an lens that has a focal length less than 50MM on a full-frame camera.
• A Normal Lens has a focal length of 50MM.
• A Telephoto Lens (aka LONG) has a focal length longer than a normal lens.

What does focal length mean exactly? It is roughly referring to the viewing angle. The wider the lens, the more you can see of the scene, while a telephoto lens (long lens) is magnifying the scene more so you see less of the scene.

Zoom vs. Prime:

1. A zoom lens is one that allows you to zoom in and out while standing in one place. Zoom lenses have two MM numbers on them. Common examples are 12-24MM, 16-35MM, 24-70MM, 24-105MM, 70-200MM, 18-200MM for example.
2. A prime lens has only one focal length and you have to move either your subject or your body to change what you see through the lens.
3. A micro (macro) lens is a lens that allows you to get really close to the subject and take an image at 1:1 magnification. These lenses can also be used for normal subjects.

Putting that information together with focal length you have wide angle zooms (12-24MM is one example), telephoto zooms (70-200MM is one example) and standard zooms (24-70MM for example).

On the prime side you have wide angle primes (a 24MM, 28MM, 35MM for example), a normal prime (50MM), and telephoto primes (85MM, 105MM, 135MM, 200MM, 300MM are examples).

A super-wide prime is a fisheye.

Fixed vs. Variable Aperture:
A fixed aperture lens has a steady maximum aperture that is not dependent upon the focal length while a variable aperture lens has maximum apertures that are affected by the focal length.

You can find the aperture information on a lens right after the focal length information:

24-70MM F/2.8 (fixed aperture) vs. an 18-55MM F/3.5-5.6 (variable aperture). If the f-stop (F/#) is a single number, it is a fixed aperture lens. If the f-stop is a range of numbers it is a variable aperture lens.

By definition, all prime lenses are fixed aperture.

Putting it all together: (the ah-ha moment!)

• A 12-24MM F/2.8 is a wide-angle, fixed aperture zoom lens.
• A 50MM F/1.4 is a normal, prime lens.
• A 70-300MM F/3.5-5.6 is a telephoto, variable aperture zoom lens.

Why is this important and why are fixed aperture lenses SO much more money?

In fixed aperture lenses there are floating elements that allow for the aperture to remain constant while you zoom (generally allowing up to one F-stop difference in exposure from the minimum focal length to the maximum). These floating elements are more difficult to make and heavier and more desired so they cost more (in some cases a LOT more).

Fixed aperture lenses are desirable because most photographers do not want to re-meter (change the exposure) when they zoom. For portrait photographers this is especially important because you may want a full-body shot and then a close up but you don’t want to have to re-meter between each shot. If you have children this comes in very handy because kids move FAST! Anyone who is shooting in manual or semi-manual modes may get very frustrated very quickly using a variable aperture lens.

Maximum apertures and why you want the lowest number you can afford (in general).

The lower the aperture number, the more light you can let into the lens. You can shoot in darker places and not use flash. Lower aperture numbers also allow you to shoot subjects that are in-focus with blurry background and foreground elements. (creating desirable bokeh).

Common confusing words:

Glass: Lens

Wide-open: Shooting at the maximum aperture rating for the lens (the smallest number). If you have a 50MM F/1.4 lens, shooting wide open would be at F/1.4. If you have a 24-105 F/4, wide open would be at F4 (most people don’t use this for anything higher than 4 in common discussion though).

Fast: The lower the maximum aperture, the faster the lens is. (In this case fast has nothing to do with speed of the lens, but the ability to use a faster shutter speed in low light situations). A 50MM F/1.4 is a fast prime.

VR or IS: Vibration reduction or image stabilization… the lens itself has a built in feature to reduce camera shake allowing you to shoot at lower shutter speeds.

L-glass: Canon’s nicest (Luxury) and highest quality optics. Nikon does not have an equivalent “class” of lenses by definition. Some say all Nikon glass is like “L glass” but IMO there are some winners and some not-so-much. This rating has to do with the quality of the optics.

AF vs. AF-S (Nikkor): AF lenses will auto-focus but the motor to control the auto-focus must be in the camera body. Entry level Nikons do not have a built-in focus motor (this makes the camera much lighter!). An AF-S lens will auto-focus with any current Nikon DSLR. If you have an entry-level DSLR, make sure you know if you need to buy specifically AF-S lenses. At the time I wrote this examples would be D40/D60/D3000/D5000 that must have AF-S lenses for the auto-focus to work.

DX lenses (Nikon) and EF-S lenses (Canon) – These lenses are designed for crop-sensor cameras. They will not allow for full functionality on a full-frame camera. If you are an enthused hobbyist or just starting out and have a crop-sensor camera, a crop lens may suit you well. If you think you might upgrade to a full-frame (pro) camera, you might consider saving a bit longer and getting glass that is compatible with both crop and full-frame sensor cameras. The full-frame Canon lenses are EF lenses. Full frame Nikon lenses are often abbreviated as FX (even though that acronym doesn’t exist and it is a lack of the DX classification that matters). You can use an EF lens and an FX lens on a crop sensor camera but not the other way around.

Lastly… INVEST in your glass. Bodies come and go but glass will be with you for a LONG time. Save your money and buy the best you can afford. When in doubt, buy the lowest fixed aperture lens you are considering. Do your homework. Rent it, go to a physical store and try it out (take YOUR camera with you). Consider buying used (these things don’t wear out but can be damaged) for the lower end lenses so you don’t lose so much on resale. Don’t write off third party lenses. Lot of them perform very well and they are much cheaper. (tamron, sigma…)

That all said, here are some of MY favorite lenses…

Nikkor 10.5MM 2.8 Fisheye

Sigma 30MM 1.4 HSM

Nikkor 24-70MM 2.8 Zoom

Nikkor 60MM 2.8 Micro

Nikkor 70-200MM 2.8 VRII Zoom

Do you love photography and want to learn more?  Join Clickin’ Moms… it is probably the MOST supportive place for mom’s to learn about cameras on the web.  Super talented and monthly membership is very affordable.  There are tons of tutorials just like this to get you started!