LensTip.com

Lens review

Canon EF 200 mm f/2.0L IS USM

16 August 2012
Arkadiusz Olech

7. Coma, astigmatism and bokeh

As you see in crops below the coma is not a problem here. Even in the very corner of full frame and at the maximum relative aperture the image of a diode remains circular. The situation doesn’t change after attaching the converter – the coma can still be called negligible.

Canon EF 200 mm f/2.0L IS USM - Coma, astigmatism and bokeh

The astigmatism is quite another matter - it is clearly more pronounced than the coma. Its level is perhaps not exactly high because the average distance between vertical and horizontal MTF50 function values amounts to 7.3% but it is not as negligible as in the case of the coma.


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After attaching the converter the astigmatism doesn’t change its level- officially it was 7.8% so, within the margin of error, the same as for the lens itself.

Let’s glance once again at a defocused image of a diode put in the frame centre, in the corner of the APS-C sensor and in the full frame corner as well.

Canon EF 200 mm f/2.0L IS USM - Coma, astigmatism and bokeh

It can be noticed that the light in the circles is very evenly spread. What’s more, already by f/4.0 the light circles are almost exactly the same no matter where the diode was positioned. You can expect the blurred areas will be smooth and pleasant to the eye.