Photoshop: Feathered layer masks don't render correctly in Classic or macOS Preview

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  • Updated 5 months ago
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  • (Edited)
I have reproduced a bug forwarded to me by a student, using a second machine.  Some problem occurs when PSD files are saved from Photoshop including non-trivial layer masks with the feather layer property set.  it is difficult for me to tell whether the PSD file is corrupted or whether the PSD file is misread by multiple other applications.

Steps to reproduce:
1.  Load an image in PS.
2.  Add an adjustment layer (I used brightness/contrast, and set brightness down to make the effect observable.)
3.  Set the layer feathering property on the adjustment layer to a non-trivial value, say, 50%.
4.  Paint on the layer in such a way that the mask itself is non-trivial.
5.  Save the result as PSD.
6.  Load the image into any of a variety of applications (including LR Classic and OSX Preview), note the image looks as if the layer mask was improperly computed.  

A.  I have reproduced this bug with different images.
B.  Both I am my student have reproduce this bug--each on different MacBook Pros running Catalina.
C.  The student has reproduced this bug both with graphics acceleration enabled and disabled.
D.  Images open/display correctly in Photoshop when loaded directly
E.  Images open/display correctly in Photoshop when loaded via LR's "Edit Original", even when the image does not display correctly in LR.
F.  I have not looked at the issue via any other operating system.

Catalina 10.15.1
PS 21.0.1 Release
LR Classic 9.0 Release

(edited to add omitted step for setting layer feathering property.)
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Joe Decker

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Posted 9 months ago

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Photo of John R. Ellis

John R. Ellis, Champion

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I was just troubleshooting a PSD compatibility-layer issue with Catalina's Quick Look, so I looked into this. 

The new compositing engine in PS 21 incorrectly omits an adjustment layer with a feathered mask from the compatibility layer (which other apps use to preview the PSD). The legacy compositing engine in PS 21 correctly includes the feathered adjustment layer in the compatibility layer.  This occurs with the graphics processor enabled or not, though the image using the graphics processor is a little garbled.

PS 20 always includes the adjustment layer with a feathered mask, regardless of compositing engine and graphics processor.

So the workaround is to enable Preferences > Performance > Legacy Compositing, as Jeffrey suggested.

Here's a folder with all combinations of feathered/unfeathered, legacy engine / non-legacy engine, graphics processor / no graphics processor in PS 21, with two combinations from PS 20 as well:

Note that on Mac OS 10.15 (Catalina), if the PSD wasn't saved with a compatibility layer (Maximize Compatibility), then Finder / Quick Look will pick one of the non-adjustment layers to display -- it won't do a faithful rendering of all the layers.  (Prior versions of Mac OS would display the file as all white.) So make sure you always have Maximize Compatibility set.
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Jeffrey Tranberry, Sr. Product Manager, Digital Imaging

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Thanks, John.