Canon EF 50 mm f/1.2L USM
7. Coma and astigmatism
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Most of fast 50 mm devices has significant problems with the coma and they start already in the corner of an APS-C/DX sensor. The Canon 50L fortunately fares well here. In the corner of the smaller sensor the coma is practically invisible even wide open. The situation changes completely when we pass to the full frame corner, though. The coma is distinct there and even stopping down the lens by 1 EV doesn’t help very much.
The astigmatism correction looks much better. On the small sensor it is negligible because the average difference between vertical and horizontal MTF50 values amounts to just 3%. On the full frame it increases to 7.7% but still it is a value which won’t be bothersome.
