Lens review

Carl Zeiss Distagon T* 35 mm f/1.4 ZE/ZF.2

28 June 2011
Arkadiusz Olech

7. Coma, astigmatism and bokeh

As you see in the crops below, the Zeiss 1.4/35 corrects the coma perfectly well, at least on the surface being the equivalent of the APS-C/DX sensor. When we pass to the corners of full frame, the coma becomes distinct, though. What’s more, stopping down by 1 EV influences this aberration very weakly, leaving it on almost the same level as in the case of the maximum relative aperture.

Carl Zeiss Distagon T* 35 mm f/1.4 ZE/ZF.2 - Coma, astigmatism and bokeh

When it comes to astigmatism we don’t have to think about it at all – the average difference between vertical and horizontal MTF50 function values in the case of the tested Zeiss amounts to 6% which is a low value.

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Encouraged by the „Bokeh measurement” article, published by us not so long ago on Optyczne.pl (available in Polish only), and the discussion in the comments section we decided to enlarge our tests by the photos showing out of focus diode image, taken in the range of 4 EV up from the maximum relative aperture, both in the frame centre and on its edge.

Carl Zeiss Distagon T* 35 mm f/1.4 ZE/ZF.2 - Coma, astigmatism and bokeh

As it was mentioned in that article, we don’t assume that this simple operation will allow to assess the bokeh of a lens in an unambiguous and comprehensive way. We still think that the way bokeh looks doesn’t depend fully on a lens itself but also on the kind of photographed scenery, the layout of objects and light. We also don’t intend to assess whether or not the photos of the out of focus diode look well or bad – it is really a matter of personal preferences.

However, photos like those above will be published anyway so everybody can see on their own how the light layout in the fuzzy diode image looks, how it is distorted, how the aperture diaphragm blades look and how big their number is and, finally, how intensive vignetting is and what is its source.