Lens: Canon EF 20-35mm f3.5-4.5 USM – flawed genius.

This is another Canon EF lens that reviewers on the web seem to hate, which is why I was determined to get one for myself.

The Canon EF 20-35mm f3.5-4.5 USM is a “consumer” lens that Canon introduced in response to third parties releasing affordable ultra-wide zooms. Canon’s pro-priced, pro-grade EF 20-35mm f2.8 L zoom from 1989 was a huge hit with photojournalists and with the EF 80-200 f2.8 “magic drainpipe” helped make the EOS 1 the camera choice of professionals.

Meanwhile, back at the ranch: Tokina and other third party manufacturers realised there was a market for an affordable ultra-wide lens.

Reviews on the web (like this excellent one) identify extremely poor contrast and flare. My copy was in very nice condition externally, but when I got it home I realised it was full of haze (I thought it was fungus) to the point where it was almost opaque. I hit YouTube and found a disassembly video for the lens and got to it. While removing the rubber from the zoom ring I noticed a lot of oily grease underneath it, and more appeared as I dug further in. I managed to get the first lens group out and thankfully most of the haze was on its back element, with more on the front element of the next group. I removed the second group (that wasn’t in the video, I winged it) and found more yuck on the front element of that. All cleaned off easily, and re-assembly was relatively simple (after finding the right thread of helicoid).

I believe that the haze is lubricant from the focus and zoom helicoids, both of which still had thick gobs of it in the threads. I propose that when the lens gets hot (stored inside a car, for instance) the lubricant evaporates from the helicoids and condenses on the glass lens surfaces. This explains why so many owners of the lenses complain about poor contrast (and a reminder NOT to let your camera gear get hot).

I would like to purchase a second example of the lens to test whether my theory is correct, but cannot justify the cost at the moment. (If anybody has one for cheap, let me know.)

Build and Handling

The EF 20-35mm f3.5-4.5 USM is beautifully engineered. It has internal focussing and internal zoom, so the lens does not change size nor does the lens front rotate or extend, ever. That makes it very nice to work with POL filters. It takes 77mm filters.

The USM autofocus offers full time manual focussing, and the zoom ring has the focal lengths well spaced, with markings for 20, 24, 28 and 35mm. There is a distance window with IR focus markings for these focal lengths as well.

The lens is made primarily from plastic with a metal mount, so it is light but rigid. Most impressively, the EF 20-35mm f3.5-4.5 USM is a millimetre shorter than the EF 20mm f2.8 USM prime lens, which itself is relatively small for an ultra-wide. It is 20mm shorter than the EF 20-35mm f2.8L and even shorter than the EF 17-40mm and 16-35mm zoom lenses that followed.

Results

The images posted here are all with the lens after I cleaned it out. I deliberately chose strong backlighting as a torture-test to see how good or bad it performs under difficult conditions. I’m happy to say that while it does flare, it’s no more than any other complex zoom lens. In less tortuous conditions the images are are sharp with lovely contrast.

The images in the gallery below are a mix of digital made with a Canon EOS 5D, and analog made with a Canon EOS 630 and Ilford FP4 Plus 125 ISO film. The lens was designed for analog bodies and film, but Canon has calculated the digital lens data to correct chromatic aberration, peripheral illumination and distortion in-camera or using Canon Digital Photo Professional for post-processing raw files.

Note that in some of the images below the backlight was blindingly strong and would be a challenge for even the best lenses. During use I need to be aware of light striking the front element (a lens hood is good but not sufficient) and when necessary use my left hand to shade the sun while taking a photo.

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Conclusion

This has become my favourite walk-around lens. It replaces four prime lenses (20mm, 24mm, 28mm and 35mm) and when I go out with it I pick a focal length (say, 24mm) and spend time working with that perspective. The lens is equally good on analog film and digital bodies, which suits me because I like using both.

I’ve spent some time looking at listings for the EF 20-35mm f3.5-4.5 USM on eBay and most if not all of these lenses have some haze, some badly. Based on my experience with the lens haze, which I believe is grease form the helicoid, I recommend the lens if you buy carefully and get one that is clean, or if you can negotiate hard and have the skills, buy a hazy one for a good price then fix it yourself. I think this is a great lens to have on your camera.