No visuals to post with this, just the facts.
The Voigtlanders 12mm f5.6, 21mm f1.8, 25mm Zeiss f2.8 and V. 35mm f1.2 have noticeable vignetting, a very minor bit at the fringe of the V. 50mm f1.1 and none with the V. 75mm f1.8.
With the vignetting comes a color shift, which is consistent and to my eye seems purple. I have not checked how much the vignette and color shift may change with stopping down, but I suspect there will be some decrease.
Infinity focus is variable between the lenses. Today I took just one adapter, the Hawk heliocoid mount locked for infinity and checked each lens with its focusing ring at the infinity block. It appears that the 35mm f1.2 at wide open loses focus at 20 feet or so. The 50mm f1.1 reaches past 25 feet and all but the 75mm fall between the 35mm and the 50mm. The 75mm Classic focused on anything I could see through blocking shrubbery. Of course that in-focus zone changes with stopping down and, as you can see in my Spanish samples from the 35mm, the one with the worst wide open infinity stop distance, that exposures in good light stopped down provides all the sharpness you might want.
The test today was run with the A7R. I suspect there are many variables at play. I have acquired a number of commonly available LM to Sony E-mount adapters, including the VM close-focusing heliocoid. I have on order a new and a used Novoflex. I'll check these in the future to see if one mount is better or worse than the next.
Lastly, I was about to return the Zeiss Biogon, but changed my mind after the focus, vignette and color shift comparisons because on my monitor I saw little difference from the other wide angles--the Zeiss did focus to 25 feet wide open, of course that was f2.8 against 1.1 to 1.8 lenses. Since I had the Zeiss all packed up for return I shot a series of images, each a pair with one exposure at f2.8 and the second at f5.6. The first set was with bare glass, the second set with a B+W XS MRC 10 filter and the last set with the lens shade on.
What do you know? Wide open the image was visibly sharper without the filter. At f5.6 you could discern a slight edge, but not as much as at f2.8. There was no color difference that I could see.
As an inveterate filter user, I may have to rethink my priorities.
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