Photoshop: Split channels on large CMYK files gives glitches when converted to bitmap or saved as tiff

  • 1
  • Problem
  • Updated 3 years ago
  • Solved
  • (Edited)
This has happened to me on CS6 and now with CC on OSX running El Capitan. When I split channels on a large CMYK file the resulting files look fine, but when I convert them to bitmap or save them as a grayscale .tiff or .psd I wind up with glitched files. This does not happen if I cut and paste the channel into a new grayscale file, so I think it is a bug in the split channels code. Original CMYK file was 7393x5700 pixels

BITMAPPED WITH A HALFTONE SCREEN




SAVED AND REOPENED AS A GRAYSCALE TIFF


ORIGINAL IMAGE AFTER SPLITTING CHANNELS ( BLACK CHANNEL )
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Karl LaRocca

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Posted 3 years ago

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Jeffrey Tranberry, Sr. Product Manager, Digital Imaging

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Does this happen consistently (100% of the time) with all files or this particular file?
(Edited)
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Jeffrey Tranberry, Sr. Product Manager, Digital Imaging

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I wasn't able to reproduce this creating my own CMYK file, splitting the channels and saving a tiff of each file using the default settings in the Tiff options dialog,
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Karl LaRocca

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It only happens if the CMYK file is not flattened and split channels creates a transparency channel. I can create a new file the same size and there is no problem. Double click the background layer to make it Layer0, and the glitch manifests. I flattened the original file and now there is no glitch.
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Jeffrey Tranberry, Sr. Product Manager, Digital Imaging

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OK. The sounds like it might be the secret sauce. Let me try that.
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Chris Cox

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Ah, yeah, that is something that wasn't mentioned in previous reports.
And that tells me where the error might be...
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Karl LaRocca

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I can also send you the file I used if you can't replicate the bug, but I was able to get it to happen with a file I created in photoshop.
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Jeffrey Tranberry, Sr. Product Manager, Digital Imaging

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Official Response
That was the secret. I have a repro case now. Engineering will look into it. Thanks for your help!
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Karl LaRocca

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That's great! Also easy to work around now that I know.
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Chris Cox

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Yep, those steps (transparency, large image) were both important.
I've implemented a fix for this in the next major release of Photoshop.
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Jeffrey Tranberry, Sr. Product Manager, Digital Imaging

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Official Response