Adobe’s Broken Vignetting Correction for Leica M Cameras — Fails to Utilize the Correct Aperture
Related: Adobe, Adobe Camera Raw, Leica, Leica M, Leica M11, optics, rangefinder, vignetting
re: vignetting
Background: the Leica M cameras cannot, do not, and never did record the shooting aperture beyond a random and often wildly inaccurate guess. And if an uncoded lens (any non-Leica lens), the lens is unknown as well. Worse, Leica judged that writing an inaccurate (possibly wildly inaccurate) guess made sense.
Adobe Camera Raw offers lens correction, including vignetting correction.
Correct vignetting correction depends on the shooting aperture being correct.
What happens when the camera writes a wildly inaccurate aperture value, such as shown below, where f/2 is really f/27? Too little or too much correction results. And that’s assuming the correct lens is listed in the EXIF info, if there even is one present—but at least the lens can be selected manually, as shown.
with vignetting correction option
For coded lenses (all current M lenses), the M cameras deal with this by doing irreversible vignetting correction to the raw file, based on known properties of the coded lens. Yet the aperture cannot be known, so how that works exactly, I don’t understand. Because of that camera RAW-whacking behavior, ACR disables vignetting correction for such lenses, which is itself problematic, as the correction may be only partial.
The foregoing is actually a reason to prefer uncoded NON-Leica lenses for the Leica M11 Monochrome, such as the fabulous Voigtlander VM lenses—unalted raw with full vignetting control in ACR. Not to mention better optical performance, superior haptics, and vastly lower pricing.
With a color camera, it made sense to alter the color to handle color shading. But with a monochrome camera, Leica is terribly amiss in foisting irreversible, potentially unwanted and inaccurate correction on the user. Not smart at all.
Suggestion to Adobe
The only way that this can work correctly is to allow the user to specify the actual shooting aperture, so that the vignetting correction feature can apply the appropriate amount of correction.
