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MTF: 180mm f/2.8 APO-Elmarit-R
MTF wide open at f/2.8 shows exceptional contrast, dropping off gacefully to the corners which are still at higher levels than most lenses reach stopped down.
Stopping down to f/5.6 raises the contrast of fine structures in the corner to diffraction limited levels, with the exception of some astigmatism which increases steadily to the corners.
Stopping down to f/8 drops the contrast of both coarse and fine structures, which is an effect of diffraction. For more on diffraction, see Making Sharp Images. Still, the added depth of field yielded by f/8 might be well worth it for 3D subjects.
MTF chart
The forward focus shift observed from f/2.8 to f/4 in both the dolls example and rulers example suggests that the MTF for the 180/2.8 APO drops from f/2.8 to f/5.6 in part because of focus shift.
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Diglloyd Guide to LEICA contains in-depth coverage of Leica M system cameras and lenses, with additional coverage of Leica M Monochrom, Leica Q.
Special emphasis is placed on Leica M lenses and certain Zeiss ZM lenses.
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