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MTF: 90/2 APO-Summicron-R ASPH
MTF wide open at f/2 is very good, but a bit low in contrast compared to stopping down 1-2 stops.
Stopping down to f/2.8 raises contrast nicely for both coarse and fine structures, with f/5.6 bringing very high micro contrast and exceptional sharpness to the extreme corners.
Focus shift
MTF at close range is strongly influenced by a substantial focus shift. Care should be taken to focus with the lens stopped down slightly (f/2.8) to partially mitigate the focus shift (focus at f/2 if shooting at f/2).
Without compensation for the focus shift, MTF will be impaired over that indicated in the MTF charts for infinity.
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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.
- Make better images by learning how to get the best results right away.
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- Real world examples with insights found nowhere else. Make sharper images just by understanding lens behavior you won’t read about elsewhere.
- Aperture series from wide open through stopped down, showing the full range of lens performance and bokeh.
- Optical quality analysis of field curvature, focus shift, sharpness, flare, distortion, and performance in the field.
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