Canon EF 28-105mm f/3.5-4.5 USM - Review / Test Report - Analysis
Lens Reviews - Canon EOS (APS-C)

Distortion

The lens shows slight barrel distortion at 28mm changing to slight pincushion distortion at the long end. At around 40mm the level of distortion is negligible.

28mm:

50mm:

105mm:

The chart above has a real-world size of about 120x80cm or 40x the focal length. Expect more distortions towards closer focus distances.

Vignetting

Typical for full format lenses on APS-C DSLRs vignetting is no big issue thanks to taking advantage of the sweet spot of the lens. It is unlikely that vignetting can be a problem even at wide-open aperture but in super critical situations you may consider to stop down a little in order to eliminate the remaining artifacts here.

MTF (resolution)

The EF 28-105mm f/3.5-4.5 USM is fairly unexciting regarding resolution. The center performance is decent throughout the range whereas the corners perform a little worse as usual - stopping down by 1 f-stop may be a good idea here. There're neither severe show-stoppers here nor is there something to rave about. However, it is worth to mention that the tested sample had a slight decentering flaw visible at various settings - nothing extreme but still clearly visible. Compared to fix-focals or L zooms the contrast performance is also fairly low so you may miss an extra color kick at times.

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 (CAs)

Chromatic aberrations (color shadows at harsh contrast transitions) are a relatively minor problem with this lens with an average pixel width of less than 1 pixel except at 28mm beyond f/8 (see also the left roof in the last sample shot below).




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