The Canon 20-35mm f3.5-4.5 has been around for a while, so as it is essentially a film camera lens, it shouldn’t have any trouble covering the full frame 5D sensor.
I decided to write up the 20-35mm / Canon EOS 5D lens test first, as this, to me, covers the most important area in my decision whether or not to buy a 5D - ultra wide angle lenses. I’m quite happy with the results from my 20D’s 8mp sensor except when it comes to wide angle lenses. I really like shooting with super wide angles, but, because of the multiplying effect of the smaller sensor it’s difficult to get the same sort of range I was used to with film cameras. Even the Sigma 15-30 I used with my Nikon camera bodies just wasn’t that wide - only equivalent to about 24mm with film. Canon have tackled this problem in two ways - you can buy the Canon EFS 10-22 and stick with the smaller sensor or you can buy a 5D or a 1Ds Mk2 where a 20mm lens is ... em.. a 20mm lens.
Unfortunately EFS lenses can only be used on certain cameras, so, if you buy the 10-22 EFS, and then decide to upgrade from a 20D to a 5D, you’d have to sell the EFS lens and start again, because EFS lenses can’t be used with any full size sensor camera body.
The Canon EF 20-35mm f3.5-4.5 USM has been one of my favourite Canon lenses for a long time. It’s performance with the Canon D60 was one of the decisive factors in my decision to go digital 4 years ago. In the hand it feels very well made with a silky smooth zooming action - no stiff uneven movement here. That coupled with the silent and instantaneous USM focusing make the lens a pleasure to use.
As this test is so important to me, and I’m sure many others, I’m going to make and publish my most detailed test yet. Apart from the usual areas of image sharpness there are other big areas of interest relating as much to the camera’s performance as to that of any particular lens. The main issue relates to the sensor’s ability to deal with light hitting it at very oblique angles. Something film, with an incredibly thin sensitive coating, could deal with without too many problems. Digital sensors, however, work best with light falling more or less straight on to them. Digital imaging sensors are covered in tiny lenses to focus the light on to the individual photosites - This makes it hard for them to capture light falling at very oblique angles, which, unfortunately is exactly what happens with most ultra wide lenses - like the Canon 20-35mm f3.5-4.5. So is there a problem?