According to lenstip, the 40mm (lateral) CA is half that on FF than it is on APS-C. Nonsensical, it seems.
They (almost) always get higher CA on APS-C than on FF. Even with the same lens tested on the same body.
Could they have simply mixed up red and blue dots?
I was inquiring: with such massive distortions, after correction, some cropping is necessary, it's always a 24mm lens but does it keep the same angle coverage ??
Just a note, for such a lens it's distortions correction that will remove corners vignetting as it is cropped out rather than vignetting correction.
(03-25-2021, 05:02 AM)toni-a Wrote: [ -> ]I was inquiring: with such massive distortions, after correction, some cropping is necessary, it's always a 24mm lens but does it keep the same angle coverage ??
Just a note, for such a lens it's distortions correction that will remove corners vignetting as it is cropped out rather than vignetting correction.
A 24mm lens with strong barrel distortion has a wider FOV (diagonally) than a well corrected lens. Correcting the image will give a similar FOV than a well corrected lens, but will lose resolution.
(03-25-2021, 05:48 AM)Brightcolours Wrote: [ -> ] (03-25-2021, 05:02 AM)toni-a Wrote: [ -> ]I was inquiring: with such massive distortions, after correction, some cropping is necessary, it's always a 24mm lens but does it keep the same angle coverage ??
Just a note, for such a lens it's distortions correction that will remove corners vignetting as it is cropped out rather than vignetting correction.
A 24mm lens with strong barrel distortion has a wider FOV (diagonally) than a well corrected lens. Correcting the image will give a similar FOV than a well corrected lens, but will lose resolution.
Thanks, make a lot of sense, the funny thing is that distortions correction is very effective on vignetting !!!! the dark area is simply cropped out I guess it is better to activate both vignetting and distortions correction
(03-24-2021, 03:55 PM)Rover Wrote: [ -> ]They (almost) always get higher CA on APS-C than on FF. Even with the same lens tested on the same body.
Could they have simply mixed up red and blue dots?
I assume it's because of the scale they use (%). Question is: percent of what? Image size in some way seems plausible (I didn't find an explanation of the scale on their site), in that case it would seem possible that the percentage values on crop are higher than on full frame if the absolute CA values are similar.
(03-26-2021, 10:35 AM)mst Wrote: [ -> ] (03-24-2021, 03:55 PM)Rover Wrote: [ -> ]They (almost) always get higher CA on APS-C than on FF. Even with the same lens tested on the same body.
Could they have simply mixed up red and blue dots?
I assume it's because of the scale they use (%). Question is: percent of what? Image size in some way seems plausible (I didn't find an explanation of the scale on their site), in that case it would seem possible that the percentage values on crop are higher than on full frame if the absolute CA values are similar.
CA gets worse the further you get from the center. So, if it is percentage of image height/width, CA should be similar for FF and APS-C. Not worse for APS-C than for FF...
(03-26-2021, 01:44 PM)Brightcolours Wrote: [ -> ]CA gets worse the further you get from the center. So, if it is percentage of image height/width, CA should be similar for FF and APS-C. Not worse for APS-C than for FF...
Yes, if it's a linear relation. But if they don't explain the scale, that's impossible to judge.