Canon EF 15mm f/2.8 Fisheye - Review / Test Report - Analysis
Lens Reviews - Canon EOS (APS-C)

Distortion

Well, a fisheye is a fisheye is a fisheye. I can´t even provide hard distortion figures here because the analysing tool didn´t like the fisheye effect on the grid chart. Anyway, the image below should give you an idea. Even with the reduced image field of an APS-C DSLR this is no mainstream lens regarding distortion.

Vignetting

The amount of vignetting was a little tough to measure due to the nature of the lens so take the chart below as a rough guidance only. At wide-open aperture vignetting is a little more pronounced but not really an issue anymore at smaller apertures. So nothing special here anyway.

MTF (resolution & chromatic aberrations)

The lens performed amazingly well in the lab. Regarding the age and the quite conventional design I had expected a much worse performance but the center resolution is already excellent straight from the max. aperture setting (f/2.8). The borders are also quite usable (in fact very good-) wide-open and improve further towards medium apertures. Overall very impressive.

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

Unlike with most mainstream ultra-wide lenses chromatic aberrations are quite well controlled which is surely a result of the simple design. That said the amount isn't totally negligible at about 0.8 pixels throughout the aperture range.

Due to it rather extreme depth-of-field a bokeh can only be observed at very close focus distances. If forced to produce a blurred background it does a decent job though you may find 5 edge shaped aperture ghostings which aren't that perfect.

The extreme field-of-view combined with the large front element and minor lens hood makes the lens quite vulnerable to flare. The situation is not too bad here but you will experience ghostings as soon as there a strong light source in the image field. The deterioration of contrast in such situation still remains within acceptable limits though.




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