Lens review
Canon EF 20 mm f/2.8 USM
4. Image resolution
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!

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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?
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