CMY data in PDF for JPEGs [do have workaround, but just curious]

[Steve Rickaby]

I know I'm using up all my tokens here, but...

FrameMaker 7 -> .ps -> Distiller 6 -> PDF.

Book contains many JPEGs. Book is to be printed in grayscale, so needs to have no information in C, M and Y channels. JPEGs converted to 256-bit grayscale, using the same workflow as I've used successfully many times before. Developer of graphics editor (Thorsten Lemke, GraphicConverter) looks at JPEG samples and swears they contain no color data (and he should know - he's been developing GC for maybe 20 years).

JPEGs inserted into FrameMaker and output as .ps, then distilled. In the PDF, JPEG images have data in C, M and Y channels

Anyone have any idea how this could happen? The last time it did, I had to send pre-press files off to someone who had the latest Acrobat for pre-press fixup. Lemke says FrameMaker is putting the color in!

Setting the printer driver to output grayscale only does not fix this - although it does map other color such as colored text to the K channel. 

What does fix it is converting the JPEGs to TIFFs.

As my pal in Ohio is fond of saying, 'Go figure!'

-- 
Steve