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

[Davis, David]

Not wanting to be contrary here, but why does the PDF have to be only grayscale, just because it's going to be printed in black and white? Surely the printer driver should be perfectly capable of making intelligent decisions about converting the colours to grey.
(And, indeed, it will make better decisions than you can earlier in the chain, cos it will know more about the output device).

I mean, for instance, any domestic or office printer in existence will happily print in greyscale if you feed it a colour file (there's usually a checkbox somewhere in the print dialog). I'm sure most of us do and see this every day.  I appreciate some things look better than others when neutered like this (some hues of colour won't give very good contrast against each other in grey) ... but the remedy for that is more in choosing the colours in the first place, not in some fancy 'conversion to greyscale' process. For instance I can't think that green text on an orange background is ever going to be very clear in greyscale, no matter what point in the chain you convert it.

David


Message: 2
Date: Wed, 11 Dec 2013 21:13:14 +0000
From: Steve Rickaby <srickaby at wordmongers.demon.co.uk>
To: framers at lists.frameusers.com
Subject: CMY data in PDF for JPEGs [do have workaround, but just
	curious]
Message-ID: <p06240810cece7f512aa9@[192.168.0.4]>
Content-Type: text/plain; charset="us-ascii"

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 


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