Maciej Patelczyk

Right, so this is the second approach. Unfortunatelly this is done using acylic glass with heavy overcast sky. Can't figure out anything better than that in my environment. I have checked it agaist several pictures and did not observe any overcorrection. My 20mm closeups of flowers look good. Measurements are for: minimum focus discance - 0.2m , 0.4m, 1.2m and inf. 0.4m is like 33% of scale and 1.2m is near inf (like 75%) for both lenses. Full range of the aperture values are covered.

Right. This is the one thing I completly forgot. One more question. If I intend to do the measurements for various focus distances does it mean that I could stand in one place and change simply the focus distance having image more or less blurred (as for initial measurement focused on infinity)?

Your suspicions were correct. At minimum focus distance applied vignetting correction reveals artificially increased luminance of the corners. It doesn't seem right. It's subtle at the beginning but when post-processing the image (increase exposure, adding contrast) it becomes more and more visible. I can wait for next full overcast sky and do the same procedure with acrylic milk glass but changing the focus distance. So I will set focus to minimum and shoot with full spectrum of aperture. Then repeat...

Easier said than done. In my neighborhood I have found fresh grey mineral plaster on one small building which seemed to be perfect candidate to check the result. The elevation is quite uniform and was well lid (northen side and today there was a fog). I shot it on 1.5m distance with focus on the wall. There vignietting correction visually are correct. I'm unable to find overcorrections. L variations between corners are not greater than 5 (but in uncorrected image they also occur so the wall was not...

Sure, I will. I will shoot it RAW+JPEG and check it. Just give ma a few days.

Sure, I will. I will shoot it RAW+JPEG and check it to. Just give ma a few days.

Sure, I will. I will shoot it RAW+JPEG toJust give ma a few days.

PDF files with the graphs for both lenses.