Leica’s Dumbed-Down Lens Documentation: Distortion and Distortion Correction Absent
Related: apochromatic, distortion, distortion correction, Leica, Leica 21mm f/2 Super-APO-Summicron-SL ASPH, Leica 28mm f/2 APO-Summicron-SL ASPH, Leica 35mm f/2 Summicron-SL ASPH, Leica APO-Summicron, Leica APO-Summicron-SL, Leica M, Leica SL lenses, Leica SL3, Leica Summicron, Leica Summicron-SL, optics
re: Leica SL3 vs Sony A7R V: In-Depth Value Comparison
I have now published detailed evaluations with all five of the Leica APO-Summicron-SL lenses.
I suspect that Leica 21/2 APO-Summicron-SL ASPH will have severe distortion, perhaps as much or more as the fun-house-mirror distortion of the 28/2 APO not to mention the absurd distortion of the 35/2. I also hope to be mistaken.
If so, the distortion will be hidden by the camera (real time correction), not mentioned in the technical documentation, flagged as a required correction in the EXIF, etc.
The existence of severe distortion is bad enough, but to hide it from customers is far worse.
Leica will surely publish its usual technical note showing MTF without regard to the required distortion correction, which degrades MTF for fine details. IMO, that is worse than misleading and dishonest.
- Leica no longer publishes distortion charts for lenses, or at least not for Leica SL lenses.
- Leica technical documents for lenses omit all discussion of distortion and distortion correction and how it affects MTF.
- AFAIK, Leica publishes theoretical computed MTF, not MTF measured with real lenses.
- Leica fantasy MTF charts do not reflect the losses in high-frequency MTF from distortion correction.
LEICA: please advise if I am incorrect on ANY of these points.
Consider that: a technical graph showing what cannot be with real pictures as any user could/would use it.
Specifically, when distortion correction is flagged by the camera as required and the camera always corrects it, and raw converters enforce it as well, there is a term for that, and it starts with "fr". Oh, and the graph is computed, not measured with real lens.
What I ask of Leica and all lens manufacturers: be honest about your optical design. Publish distortion charts, and publish MTF with and without distortion correction. Say explicitly whether distortion correction is required. Pretty simple. That’s what an honest company would do.
Below, Iridient Developer is one of the rare raw converters that allows disabling required EXIF flags eg distortion correction.
LEICA SL3 + Leica 35mm f/2 Summicron-SL ASPH
[low-res image for bot]
