TIFs with alpha channel displaying incorrectly

Storebridge

• 2012年12月18日 22:05

Hello,

This problem occurred in Expression Media as well, and we still haven't solved it.

We got a bunch of scans back after a book went to publication. The images are CMYK TIF files. They don't have multiple layers.

In MediaPro, they display in both thumbnail and media view as a yellow rectangle, or in some cases part of the image shows up but the rest of the image is yellow.

I've found some information in the old iView PDF Help file* indicating that the problem is related to the presence of an alpha channel, or possibly due to having 2 alpha channels. I tried the troubleshooting measure recommended, but it didn't work.

I do get a correct display in MediaPro if I open the file in Photoshop and save a copy with Alpha Channel DESELECTED in the Save As dialog.

QUESTIONS:

1. Is there a way to get MediaPro to display the existing images correctly without having to resave them all?

2. Am I losing important info if I do end up having to resave all the images this way?

*Here's what the Help item says:
"Alpha channel in Photoshop file incorrectly displayed (typically yellow).
Some Photoshop documents with alpha channels can be incorrectly displayed. MediaPro sometimes interprets the alpha channel as a transparent layer. MediaPro displays transparencies as a specific color and by default this is yellow. See example in Figure 3.3.
To correct this, turn on the Use Alpha Channel setting (Figure 3.4) in the Preferences › Media Rendering › Images dialog.
All newly imported Photoshop files will be displayed properly. To correct existing thumbnails you need to select them and choose Rebuild Item in the Action menu."

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  Storebridge

  • 2013年01月08日 16:05

  Following up. I posted a trouble ticket in the Phase One support system and was asked to upload an example file, which I did. Here is the response I received:
  
  

  
  I can verify that there is a "Blu Copia" named channel in the file. Unfortunately this channel is unavoidable by almost every software that encounters it and, most importantly, it cannot be ignored by the Apple Operating System which would be the only Render Engine that could potentionally be used as a workaround for the files display in Media Pro.
  Based solely on the nature of the file and the existence of this channel, the display will always be as depicted in the attached files for all previews.
  
  I apologize that we cannot be of further assistance.
  
  Kind Regards,
  Phase One Support
  

  
  
  
  I'm SOL!

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• 

  Permanently deleted user

  • 2013年02月01日 21:43

  There is a setting in preferences you can change to get rid of the yellow transparent alpha channel from thumbnail.
  Preferences>Media Rendering...
  (shift-command-,)
  
  select Images Tab
  Uncheck Use alpha channel
  
  Then with thumbnail(s) selected.
  Action>Rebuild Item
  (command-b)

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• 

  Storebridge

  • 2013年02月04日 21:32

  Hi Laurie,
  
  Thanks for the reply. Indeed, I had already tried both selecting and deselecting that checkbox, but it has no effect on the thumbnail. Changing the color swatch does change the yellow-colored area of the image to the new color, though.

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  rmoorlag

  • 2013年02月04日 22:44

  I had already tried both selecting and deselecting that checkbox, but it has no effect on the thumbnail

  
  The effect will only apear after rebuilding the thumbnails:
  

  Then with thumbnail(s) selected.
  Action>Rebuild Item
  (command-b)

  
  Roelof

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  Storebridge

  • 2013年02月05日 15:05

  Thanks Roelof -- I'm aware of that. Rebuilding the thumbnails after either selecting or deselecting the "Use Alpha Channel" preference setting has no effect.
  
  I checked to make sure the thumbnails are actually rebuilding by changing the transparency color swatch to a different color. On rebuilding, the yellow areas of the thumbnail change to the new color, so I know the rebuild is occurring, it's just that the alpha checkbox isn't doing anything one way or the other to these thumbnails.
  
  As the reply from Phase One suggested, the thumbnail display of these images in the Finder is similarly off.

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  Storebridge

  • 2017年10月12日 21:35

  Five years later, we have a minor update.
  
  I resorted to saving a second copy of these files with the additional alpha channel deleted. On importing the duplicate file, the thumbnail is correct. Obviously it's annoying to have to maintain two copies of essentially the same file, but it is a solution.
  
  Here's the update: Since I was going to the trouble of making a duplicate copy anyway, while in Photoshop, I used the Edit menu / Convert to Profile to convert the color space to the working RBG space. As mentioned in the original post, the TIFs came to us as CMYK since they were going to be printed in a book. Since we were saving the original files separately from the new dupes I was making I thought I'd take the opportunity to convert to RBG, which is our default.
  
  I accidentally saved one in RGB without first deleting the extra alpha channel. When it imported into Media Pro, the thumbnail displayed correctly, even though it still had the extra alpha channel.
  
  So for some reason the alpha channel is not problematic within this RBG color space. Weird!

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