Canon EF 24-85mm f/3.5-4.5 USM - Review / Lab Test Report - Analysis
Lens Reviews - Canon EOS (APS-C)
Article Index
Introduction
Analysis

Distortion

The lens shows some very strong barrel distortion at 24mm changing to slight pincushion distortion at 50mm and 85mm.

24mm:

50mm:

85mm:

As usual you should probably expect more distortions towards closer focus distances.

Vignetting

The EF 24-85mm f/3.5-4.5 USM is a full frame lens so it can take advantage of a sweet spot effect on APS-C DSLRs and it shows. Vignetting is basically a non-issue with this lens at any focal length even at wide-open aperture.

MTF (resolution)

As hinted above the EF 24-85mm f/3.5-4.5 USM received some rather mediocre reviews during the mid ´90s. However, all these reviews were based on full frame analysis. When looking at the original Canon MTF figures the lens is very good except at the borders. On APS-C DSLRs the borders reside way beyond the cropping factor and this also shows up in the Imatest measurements. On the EOS 350D the lens is capable to deliver a very good to even excellent center performance combined with marginally worse borders. Very impressive and basically as good as the pro-grade EF 24-70mm f/2.8 USM L (again: just on APS-C DSLRs).

Below is a simplified summary of the formal findings. The chart shows line widths per picture height (LW/PH) which can be taken as a measure for sharpness. If you want to know more about the MTF50 figures you may check out the corresponding Imatest Explanations

Chromatic Aberrations

During the MTF analysis it became obvious that chromatic aberrations (color shadows at harsh contrast transitions) are a weak spot of the lens. At the image borders the problems almost reaches 2 pixels on the average at 24mm at f/3.5. Quite bad. However, the issue decreases rapidly towards medium aperture settings where the lens is more in line with the rest of the gang. At 50mm the problem is still quite pronounced, less so at 85mm.

Verdict

The Canon EF 24-85mm f/3.5-4.5 USM exhibited a quite mixed performance. On the upside the lens is very sharp with very little vignetting throughout the range. Unfortunately distortions at 24mm are pretty hefty as are chromatic aberrations. The build quality is pretty decent and the AF performace is a joy. All-in-all the lens is capable to beat the cheapo EF-S 18-55mm as well as the EF-S 17-85mm IS and regarding sharpness it can even rival the the EF 24-70mm f/2.8 USM L (on APS-C). If the focal length range was more attractive here the lens would have been a killer but as such it is just a good compromise.

Optical Quality:    
Mechanical Quality:
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