Canon Lens Test

I thought I'd try testing the performance of the lenses on my Canon EOS 40D. I used an EIA resolution chart printed A4 size and pinned up outside. Where possible I took a photo of the A4 sheet full screen. The only instance where this was not possible was with the 17-85mm lens at 17mm, where it was not possible to focus close enough. Each lens was tried at the extremes of its zoom and aperture. The images below are the cropped centre of the results.

The lenses used were the Canon EF-S 17-85mm f/4-5.6 IS USM, the Canon EF 70-300mm f/4-5.6 IS USM and the Canon EF 500mm f/4L IS II USM.

The table below gives the results.

17 mm Focal length, F4

17 mm, F22. Note that the magnification at F22 seems to differ from F4

85mm, F5.6

85mm, F22

70mm, F4

70mm, F32

300mm, F5.6

300mm, F32

500mm, F4

500mm, F32

Conclusions on the initial tests

The more expensive lenses have better performance! On the result of these tests, it's notable that the 500mm lens gives about the same resolution as the 17-85, but from about 6 times away. Not bad. It's also notable that the resolution stopped down is worse for all the lenses - a result of diffraction limited resolution.

Further Tests

I've swapped the EOS 40D for an EOS 7D, which has a higher resolution sensor, and bought a Canon EF 70-200mm f/2.8L IS II USM together with two teleconverters (range extenders, in Canon-speak): the Canon Extender EF 1.4x II and the Canon Extender EF 2x III. The table below gives the results of repeating the tests with these lenses. I spent a little more time trying to optimise the printing of the test pattern before taking the photos, so the best may look a little different from those above.


Wide open




17-85mm @ 85mm

24-70mm @ 24mm

24-70mm @ 70mm
70-200mm @ 70mm

70-200mm @ 200mm

70-200mm @ 200mm
with 1.4x teleconverter

70-200mm @ 200mm
with 2x teleconverter