Canon EF 40 mm f/2.8 STM review - Coma, astigmatism and bokeh

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Canon EF 40 mm f/2.8 STM

7 August 2012

Arkadiusz Olech

7. Coma, astigmatism and bokeh

When you take photos using a small APS-C sensor the coma shouldn’t be a problem at all. In the corners of full frame that aberration becomes more distinct but only at the maximum relative aperture. On stopping down to f/4.0 you see the coma reduced to a low level. No serious complaints in this category.

Canon EF 40 mm f/2.8 STM - Coma, astigmatism and bokeh

The astigmatism results look even better. The average difference between horizontal and vertical MTF50 function values amounted to just 0.6% which is a truly sensational value.

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The light layout in off-focus diode images should be also described in very positive terms. We can observe very nice circles in which the light is evenly spread without any noticeable local extremes. It suggest that the fuzzy areas in our photos will be pleasant to the eye.