Canon Lens Buying Tips

Understand the Confusing Nomenclature

You're taking great shots with your new Canon DSLR. Landscapes, buildings, portraits of your family and friends: The camera rarely leaves your eye. But, you're feeling a little limited, hemmed in with the kit lens that came with the camera body. After a quick look at the Canon lenses online you find yourself lost in bizarre nomenclature.

Canon EF 70-300 f/4-5.6 IS USM
Canon EF-S 17-55 f/2.8 IS USM
Canon EF 50 f/1.4 USM
Canon EF 24-105 f/4L IS USM

What? What does that mean? I'm not a professional, only a studious shutterbug. What's EF and EF-S? What is IS and USM? Fear not, Canon lens nomenclature is not as hard as it seems. Let's break it down.

EF
The SLRs in Canon's EOS line can accept EF or EF-S lens. The letters identify the type of mount on the lens. EF stands for Electro-Focus: An autofocus system that uses only electronic contacts between the camera and lens, not gears or levers. The EF lens and its bayonet-style mount were introduced by Canon in 1987, and replaced the long serving FD mount.

Simple, just a name. If you have a Canon EOS camera, you use an EF lens.

But, what about EF-S?
Not all Canon DSLRs are created equal. There are two main categories of DSLRs: Full frame and APS sensors. Great, more terms. There's not a lot here you have to know, unless you really want to. Only two of Canon's DSLRs have the larger full frame sensor: The 1D and 5D models. These top-of-the-line camera bodies will only accept EF lenses.

EF-S lenses are made for Canon's other bodies that lack a full frame sensor. The S stands for short back focus. The back of an EF-S lens projects further into the camera body, is closer to the sensor, and provides for better wide-angle shots.

You can use an EF or EF-S lens on APS sensor Canon bodies, but you cannot use an EF-S lens on a full frame body (EOS 1D or 5D). Canon has made it impossible to mount the wrong lens on the wrong body. Because an EF-S lens projects further into the body, using one on a full-frame sensor camera would result in damage to both the lens and camera.