Why does focus stacking create a blotchy background in macro flower photos?
Asked 7/17/2016
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2 answers
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I’m shooting macro flower photos with a Canon 50D and combining multiple frames in Photoshop CS5 to increase depth of field. The flower itself comes out sharp, but the out-of-focus background becomes patchy or blotchy, with different areas apparently pulled from different source images. I understand some edge distortion can come from alignment and can be cropped, but why is the background breaking up like this? Is this a normal focus-stacking artifact, and is there a way to fix it in Photoshop?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
10y ago
2 Answers
1
Without seeing your layer masks I can't say for sure, but it looks like the auto-masking is combining out-of focus backgrounds. I recommend reading about layer masking; then, clean up the masking so that only one layer is used for the background.
This video is an overview: https://www.youtube.com/watch?v=gIh4v4RPQ70
At around 2:54 in the video it shows the auto-generated masks. Almost all automated image combination tools require manual clean up.
Originally by user40058. Source · Licensed CC BY-SA 4.0
user40058
9y ago
0
Generated from our catalog & community — verify before relying on it.
Yes—this is a common focus-stacking artifact. Photoshop’s auto-align/auto-blend masks can mix different out-of-focus background areas from multiple frames, which makes the background look patchy. Any subject or background movement, even a slight breeze, can make it worse.
The usual fix is manual cleanup: inspect the generated layer masks and edit them so the background comes mostly or entirely from a single frame, rather than from many frames. If needed, finish with the clone stamp or healing brush to smooth remaining blotches.
In this kind of flower shot, focus stacking may not help much if your goal is simply a sharp flower with a soft background. Stopping down the lens may give enough extra depth of field while keeping the background pleasantly blurred.
If you want a cleaner background, using a simple solid backdrop behind the flower can also help.
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