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Lens review

Canon EF 24 mm f/2.8 IS USM

17 October 2012
Szymon Starczewski

4. Image resolution

The resolution test of the Canon EF 24 mm f/2.8 IS USM was based on RAW files from the Canon EOS 1Ds MkIII body. In the case of that camera the decency level is situated near 30-32 lpmm and the best fixed-focus lenses can get as high as 44-46 lpmm.

Let’s glance at a graph below to assess how the tested lens fares in the frame centre, on the edge of the APS-C sensor and on the edge of full frame.

Canon EF 24 mm f/2.8 IS USM - Image resolution


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A great performance in the frame centre sticks out immediately. Even at the maximum relative aperture the image is very sharp – the resolution result you see there, amounting to over 41 lpmm, is simply sensational. It is worth emphasizing that by f/4.0 you get to a very high level of 44 lpmm. It is really a huge achievement if you take into account the fact that the fastness of the lens means the f/4.0 aperture, where you usually have record values, is in the distance of just 1 EV from the maximum relative aperture. In that very short distance of just 1 EV the lens can “lose” most of serious optical aberrations. I am very curious how this lens would fare if it was just a bit faster. Even f/2.5 aperture might cause it to be a far juicier morsel for the owners of f/2.8 zoom lenses and by f/4.0 the result could come close to the record values of 45-46 lpmm. Ok, let’s end the speculations here and return to the facts.

The performance on the edge of the APS-C sensor can be only praised. Even at the maximum relative aperture the image is fully useful and its quality becomes good on stopping down. The edge of full frame is problematic, though - to get a fully useful image, you must apply f/5.6 aperture. To tell you the truth I thought the full frame performance would be an asset which might make the owners of zooms purchase that “prime”. Such lenses as the 24–70 mm f/2.8 or the16–35 mm f/2.8 are instruments difficult to construct and the quality of images they provide at the maximum relative aperture on full frame is never especially good. On the other hand if you deal with an expensive “prime” you should be more demanding. Unfortunately the EF 24 mm f/2.8 IS USM doesn’t deliver here.

At the end of this chapter we present some crops taken from photos of our test chart, saved as JPEG files with the lowest sharpening level.

Canon EF 24 mm f/2.8 IS USM - Image resolution