Studio Tests - APS-C format
The Canon 50mm F1.8 generally gives a pretty good account of itself on APS-C, marred only by soft corners at wide apertures. Aside from that the lens does very well, matching the EF 50mm F1.4 USM at common apertures and possibly even a bit sharper in the centre. It's much sharper than any of the EF-S zooms we've tested, for example it's simply streets ahead of the 18-55mm F3.5-5.6 IS kit lens.
|Sharpness||The Canon 50/1.8 is quite sharp in the centre wide open, but the corners are noticeably soft, and the lens needs to be stopped down to F3.5 when sharpness in these regions is important. Best results are obtained at F5, and beyond this diffraction slowly takes its toll; as usual on APS-C, anything smaller than F16 should be treated as emergency only.|
|Chromatic Aberration||Lateral chromatic aberration is essentially a non-issue (a fundamental characteristic of the symmetric Gaussian design of the lens). There's also little sign of the blue 'colour blur' which plagues the EF 50mm F1.4 USM at wide apertures. This is about as well-behaved as you'll ever see.|
|Falloff||We consider falloff to become perceptible when the corner illumination falls to more than 1 stop less than the centre. As usual for a full-frame lens used on APS-C, there's simply nothing to worry about here.|
|Distortion||Distortion is very low at just 0.4% barrel, which will be essentially invisible in real-world use.|
Specific image quality issuesAs always, our studio tests are backed up by taking hundreds of photographs with the lens across a range of subjects, and examining them in detail. This allows us to confirm our studio observations, and identify any other issues which don't show up in the tests.
Soft corners at wide apertures
Not unusually for a full-frame optic used on the resolution-hungry APS-C format, this lens isn't at its best at wide apertures, and although central sharpness is OK the corners look distinctly soft. In this regard it's worth noting that depth of field is very shallow at F1.8, and real-world results are mainly dependant upon focus accuracy, with the slightest relative movement between photographer and subject resulting in a misfocused image. Of course depth of field issues also mean that the corners of the frame are often out of focus at F1.8 anyway.
Nevertheless, to illustrate this issue here's the latest in our series of educational brick wall pictures. At F1.8 the centre looks a little soft and lacking in detail, but the corners are very soft indeed. Stopping down to F4 improves things dramatically - the centre now looks extremely sharp with well-resolved fine detail, and the corners have also improved significantly (stopping down a little further to F5.6 extracts the best possible performance).
|Canon EOS 450D||Canon EOS 450D|
|100% crop, centre of frame||100% crop, centre of frame|
|100% crop, top left corner||100% crop, top left corner|