RGB PDF file forced into CMYK colors when transparency used

[Bartek_Podkowa@adobeforums.com]

I've had a problem since InDesign 2.0 (still in CS) with producing PDF file in RGB color space. Everything is OK until I use a psd file with transparency placed in InDesign. In such a case the page icon on the pages pallet is indicating, that transparency has been used (as it switches into transparency checkerboard pattern). Of course I have to set the transparency blending space (global) for the document into RGB (what I sure do) and then in InDesign itself the colors look great. However at the time of PDF export the color are force into the CMYK gamut what I can see it the resulting PDF file. I tried various PDF setting and versions, and forcing RGB color space to no avail. Without the transparent objects the problem does not exist.

Has anybody found any cure for it?
Bartek

[Bob_Levine]

Do you have RGB selected for the color space in the PDF export?

What did you do to check the color mode in the PDF?

Bob

[Steve_Werner@adobeforums.com]

Also how are you creating the PDF--by direct export? by creating a PostScript file and Distilling? Have you tried both methods? Exactly what settings are you using?

[Bartek_Podkowa@adobeforums.com]

I export PDF via eithe direct export or PDF Printer from Acrobat 6 Pro (previously Distiller). In both cases I set either RGB space or "Leave unchanged" in PDF options what should result in the same.

I check the colors just with my eyes as I can clearly see the gamut change and "dirty colors" of CMYK gamut. If I have the multipaged document then the color shift occurs only on those pages using transparent bitmap but not theothers. WhenI delete the objest with transparency the rest of the page is starting to export corectly.

I streamline the color settings in all Adobe apps and monitor profile to Adobe RGB 1998. Looks like small bug in InDesign's transparency management or PDF display of the bitmap object using the mask with transparency.

Have you ever reproduced it?
Bartek

[tmalcom@adobeforums.com]

I just encountered this same problem developing an IDCS template for producing PDFs. In putting a fill color in some table cells, the RGB color was converted to CMYK (and looked horrible). I had already set every color space I could find to Adobe RGB, but the color would still shift to CMYK. It was only Bartek's post the pointed me in the right direction. I have a placed PSD logo that has transparency, which was obviously (well, now it's obvious anyway) causing the problem...but that's the last thing I would have suspected. I changed the Transparency Blend Space to RGB and now the color doesn't change. I just don't understand why that one little piece would affect the entire document. Smells like a bug to me.

[Bartek_Podkowa@adobeforums.com]

...form me it's not maybe a bug, but a result of natural priority for traditional CMYK - postscript based technology that is basic for all Adobe page layout programs. The RGB support especially the transparency like behaviour is rather kind of "add-on" for this kind of applications and as such is not perfect.

After additional development of the issue I figured out that the CMYK like colors are rather generated in the level of PDF display color render, as when you open the PDF looking CMYK in Photoshop it's still RGB (wow!) and if you go under version 5 of Acrobat (save in Acrobat 4 version) the file looks great and no CMYK shift occurs.

Bartek