Why does Photoshop Photomerge fail to even out exposure in very large panoramas?
Asked 5/15/2017
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2 answers
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I’m stitching panoramas in Photoshop Photomerge and sometimes large panos show obvious exposure differences between frames, even though all images were shot in manual mode and developed with the same settings. A smaller section of the same scene stitches cleanly, but the full pano may not blend the exposure transitions well. One example used about 80 images, while a smaller successful section used about 20. I’ve also had some even larger panos work, so the issue seems inconsistent. Could this be caused by overlap, changing light, shooting time, viewing angle, or a practical limitation in Photomerge?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
9y ago
2 Answers
1
There might be a few problems that cause this:
- Overlapping: if there is not at least 20-30% overlap between images (as I can see that in the bottom ones there aren't) then lens distortion is harder for the algorithm to fix, and might be even impossible.
- Time: If it took a lot of time to take the set of images, then the lighting might have changed just enough (I can see it was a cloudy and brightly lit day so cloud movement could have made a dramatic change) to give the algorithm a hard time stitching.
- Lighting conditions: Even though you were on M mode the entire time, sometimes, lighting differences cause be viewing angle (directly to the sun or to the opposite side) might be to much for the algorithm.
My suggested attempt at a fix is to do them in small batches (since you said they work fine that way) and then stitching the batches together (either with the automated tool or by hand).
Good luck!
Originally by user98488. Source · Licensed CC BY-SA 4.0
user98488
5y ago
0
Generated from our catalog & community — verify before relying on it.
Photomerge’s blending can break down in large panoramas when the source frames aren’t consistent enough for the algorithm, even if camera settings stayed fixed.
Based on the answers, the main causes are:
- insufficient overlap: about 20–30% overlap is usually needed; less overlap makes alignment and distortion correction harder
- changing light over time: clouds moving during a long capture can create real brightness shifts between frames
- angle-to-light changes: even in manual mode, frames pointed more toward or away from the sun can look different
So this is not necessarily a memory limit. It’s more likely that the combination of many frames, scene coverage, and slight lighting changes makes exposure blending unreliable.
A practical workaround is to stitch in smaller batches first, then combine those results. Since smaller sections already work for you, that suggests the source images are usable but the full set is harder for Photomerge to normalize consistently.
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UniqueBot
AI9y ago
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