Lens review
Canon EF 100 mm f/2.8 L Macro IS USM
8. Vignetting
On the small APS-C sensor the vignetting is not a serious problem. At the maximum relative aperture it amounts to 20% (- 0.65 EV) and it decreases to an imperceptible level of 5% on stopping down by one stop. The crops below show it perfectly.
It is quite understandable that the vignetting is higher on the full frame. It would be difficult not to notice it at the maximum aperture, where its level amounts to 43% (- 1.62 EV). The result is significantly high but, as we know, on full frame even the results far above 50% are not very rare. Fortunately on stopping down to f/4.0 the vignetting decreases to 20% and by f/5.6 it becomes imperceptible amounting to only 8%.
On the full frame we notice one more interesting effect, namely a slight brightening in the upper part of the frame. It is not connected with measurement errors but it is rather a lens’s characteristic because we got that effect on every picture, no matter at what angle the lens- plus- body system was positioned to the photographed plane. This effect is rather a curiosity, not an advantage or a disadvantage, especially that it will be difficult to notice in real-life pictures.
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