Sky Color shift
I have this set of Raw images that I am stitching into a pano. I shot these images at 9:30 AM, moving from north-northwest to northeast toward the rising sun. As you can see, there is a pronounced non-uniformity in the sky between images 1 and 6. I was able to remove the color shift after stitching, but I would like to be able to achieve a uniform sky before stitching.
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Was there a uniform white balance when they were shot?
Ian
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yes, the problem was that the sky toward the sun is lighter than the sky away from the sun
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Incidentally, this set of six images is really part of an 18 image set consisting of 3 rows / 6 panels. C1 v22 did an outstanding job stitching them into a high resolution image
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It's not clear to me whether the best thing is to try to achieve a uniform sky before stitching or after. If you changed something between say Image 4 and Image 5 in your sequence, then there would be a glitch at the overlap between the two when they were stitched, perhaps. Maybe it's best to apply a linear gradient to the stitched result from right to left and change it open a graduated basis on that. After all, it does stitch it together as a raw (DNG) file, so there is still quite a lot of latitude. (As long as the last in the sequence isn't so over-exposed that highlight recovery isn't possible.
Ian
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Thank you. It was easy to make the sky uniform after stitching in C1. But when I tried to stitch in Hugin, I had to go back to C1 to make the sky uniform. When stitching in Affinity Photo, sky uniformity was much better
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Basically, you can't. The real sky varies across your image. If you try to adjust your camera (before each shot) to try to make the sky uniform in each shot (a very difficult task), then you will get a varying foreground across the shots which will be even worse.
First off, make absolutely sure that exposure is fixed when taking pano shots and do not use a circular polarizer when shooting panos. This gives the C1 pano merge engine a better chance at reproducing what you actually see.
Then, use post processing to address the sky. What you show here is a cloudless sky which is fairly easy to address in post processing. You can even use the uniformity tools in Capture One's color editor as a first pass at fixing this. Or, you could do a full-blown sky replacement in Affinity Photo or Photoshop.
You can also use a left/right gradient across the sky and address varying brightness that way.
It is possible that other pano stitchers are applying some sort of logic in the stitch to try to make the sky more uniform whereas C1 is just reproducing the variability that exists in the actual shot.
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Thank you, I was able to improve the sky using the uniformity tool the way you described. I was just hoping there was way to do it before stitching.
Affinity Photo made a decent sky directly during stitching and C1 made a very good sky after stitching via the uniformity tool.
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Apparently Affinity Photo has some sky uniformity processing as part of its pano merge logic which is certainly easier when processing a cloudless sky.
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On the other hand, Affinity doesn't give you a stitched file in a raw (DNG) format. Nevertheless, it does a good job.
Ian
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