EF 20mm f/2.8 USM
This fixed-focal length lens can be thought of as two distinct lenses: an affordable ultra-wide angle option for full-frame camera users, and conversely a moderate wide-angle lens when mounted on SLRs with 1.6x "crop factors"*, where it would act like a 32mm lens would on a traditional film camera. As such, it's an attractive option for large group photos and similar situations. Its f/2.8 maximum aperture can be a big benefit for both still and video imagery when shooting in low light.
- Especially affordable ultra-wide angle option for full-frame shooters (EOS-5D series and EOS-1Ds models), particularly when f/2.8 aperture is a factor
- Like most fixed focal length wide lenses, relatively little linear distortion: potentially valuable asset for video, where such distortion can't easily be corrected in the computer
* Cameras with APS-C size imaging sensors and 1.6x “crop factor” include EOS 7D, EOS 10D through 60D, and all versions of EOS digital Rebel