Andy Westlake finds out whether Canon’s inexpensive and tiny prime lens is a tasty option for APS-C users in our Canon EF-S 24mm f/2.8 STM Review
Canon EF-S 24mm f/2.8 STM – Image quality
For a decidedly inexpensive lens, image quality is rather good. It’s slightly weak at f/2.8, with somewhat soft corners and visible vignetting, but stop down to f/4 and the lens performs very well. Pictures are consistently sharp across the frame, and remain so at apertures down to f/11. At f/16 diffraction blurs the image a little, and at f/22 it’s visibly soft when viewed on the pixel level. Of course, there’s a trade-off to be made against depth of field here, as sometimes the increased front-to-back sharpness can be more important than any loss of acuity when considering the image as a whole.
Some barrel distortion is present, with visible bowing of straight lines along the edges of the frame, but it’s not very objectionable and is easily corrected in post-processing. Red and cyan colour fringing from lateral chromatic aberration is visible if you go looking for it, and covers a larger area of the frame than I’d normally expect. However, with relatively narrow fringe widths, it’s never really intrusive.
With its f/2.8 aperture, this Canon lens can give quite nicely blurred backgrounds at close focus distances, and in general the bokeh is reasonably attractive. Complex backgrounds can sometimes appear hard-edged and ‘busy’ when viewed too closely, but considering this lens can be bought for around £150, it seems churlish to complain.