LensTip.com

Lens review

Carl Zeiss Touit 12 mm f/2.8

30 August 2013
Szymon Starczewski

7. Coma, astigmatism and bokeh

The coma makes itself felt quite strongly at the maximum relative aperture and it contributes greatly to limiting the resolution values on the edge of the frame there. Fortunately, on stopping down by 1 EV the aberration becomes moderate.

Carl Zeiss Touit 12 mm f/2.8 - Coma, astigmatism and bokeh


The astigmatism decreases on stopping down in a truly textbook fashion. At the maximum relative aperture it is still noticeable, reaching 10%; after stopping down the aperture to f/4.0 it is reduced to a very low level of less than 3% and by f/5.6 that aberration becomes imperceptible (below 1%). The average value, on all testing charts and in a distance of 3 EV from the maximum relative aperture, amounted to 4.7% which allows us to state that the tested lens doesn’t have any problems with this off-axis aberration.

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Defocused light points don’t look perfect – in the centre of the circle you can notice a darker area and a noticeable rim on its edge. Still, due to the parameters of the tested lens and its usage, you won’t admire large defocused areas in your photos very often so it shouldn’t be a problem.

Carl Zeiss Touit 12 mm f/2.8 - Coma, astigmatism and bokeh