EXCERPT page containing first few paragraphs. 2024-04-18 00:39:42
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MTF: 135mm f/3.4 APO-Telyt-M
Wide open, performance is high over most of the frame, but stopping down to f/5.6 pops the contrast to a very high level over the central 3/4 of the frame, with a graceful drop to the edges and corners.
Since MTF f/4 is not supplied, we cannot be sure if most of the gains of f/5.6 are already present, but most likely there are some benefits to f/5.6 over f/4, not the least of which will be concern over focus error, which is almost a certainty with a 135mm lens and rangefinder focusing.
This is a very high performance, but less uniform and less good to the edges and corners as compared with the 90/2 Summicron-M ASPH. The astigmatism that is seen at f/5.6 and particularly at f/8 is apparently due at least in part to lateral chromatic aberration, as per field shots which reveal this color error on higher resolution mirrorless camera bodies.
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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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- 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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