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Lens review

Canon EF 20 mm f/2.8 USM

12 April 2010
Szymon Starczewski

4. Image resolution

There are several wide angle zoom lenses with an aperture near f/2.8 and the 20 mm focal length in their focal range available on the market. What is the point of buying a “prime” then? The answer is easy. In the frame centre zoom lenses can be as good as primes but usually they lose the duel at the frame edge.

Looking how the Canon’s 2.8/20 fares in the frame centre we know at once that we deal with a prime lens here. Even at the maximum relative aperture the lens exceeds a 30 lpmm level and already by f/4.0 a level of 40 lpmm is exceeded too. A sensational performance in short!

Canon EF 20 mm f/2.8 USM - Image resolution


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An unpleasant surprise awaits us when we look at the frame edge performance. It might give us an impression that we deal here with a classic “zoom” lens, designed for an APS-C/DX sensor, not with a full frame prime lens.

It is a very painful slip-up as it undermines the very reason we would want to buy a prime lens. If we can shot pictures of similar quality with a Sigma 18-50 f/2.8 or a Tamron 17-50 f/2.8 why should we think about buying a Canon EF 2.8/20 which costing as much as them but is definitely less universal?

Canon EF 20 mm f/2.8 USM - Image resolution