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MTF: 280/4 APO-Telyt-R
Peak performance is reached wide open at f/4, but experience with high resolution digital cameras suggests that stopping down to f/5.6 is the smart move in case of tiny focusing errors, all too easy to make. As well, f/5.6 evens out the illumination, adds a little depth of field, and is really no different than f/4 in real performance.
Stopping down beyond f/5.6 starts to drop the contrast on both coarse and fine structures according to the laws of physics (diffraction), and this is clearly seen with real images on a high resolution digital camera. For more on diffraction, see Making Sharp Images.
Astigmatism is present, but it is unclear as to what causes it, since there is no trace of color fringing. Presumably it results from other optical effects.
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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.
- Save money by choosing the right lens for your needs the first time, particularly the Summilux/Summicron/Elmarit choice and/or Zeiss ZM.
- Make better images, a sort of “cheat sheet” saving yourself months or years of ad-hoc learning. Processing parameters are discussed and shown.
- Jaw-dropping image quality found nowhere else utilizing Retina-grade images up to full camera resolution, plus large crops [past 2 years or so].
- 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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