Best Way to Export PDF for Press w/ Grayscale Images

Question

Hi, we've been trying to move to a PDF based workflow for sending files to printers if possible so that all color conversion can take place at the final step of creating the PDF. This way, all images can remain RGB in their native color space.
But I just had to create a PDF that had a mix of images in it. Some were typical RGB, some had already been converted to CMYK (probably US SWOP), and some were true grayscale images.
When I created the PDF, I set it to convert all colors to the destination profile, which in this case was just US SWOP because the printer didn't have a more specific profile to suggest (most don't). It appears that the images converted properly, but the the grayscale images are using just the K channel (which I suppose is to be expected).
A while back we printed a fully grayscale piece where all images were converted to a specially created SWOP profile that had modified GCR curves to have most of the data still represented by the black channel, but with some nice CMY thrown in as the tones deepened. The result was amazing. The images had no color cast, but were a nice rich grayscale. The printer was very impressed as well.
A) So what would be the best workflow to incorporate mixed color images, and still have the grayscale images turn out nice & rich? Do I have to convert all images manually first (trying to avoid having to do this)?
B) If the printer doesn't offer a profile, and probably doesn't fully understand or utilize color management, are we best to supply the PDF file converted to US Web Coated SWOP because that is what THEY would be most used to getting? This job, however, will be sheet-fed on a matte paper with a satin AQ.
THANKS! Any tips would be greatly appreciated. Trying to refine our workflow here.

Answer 1

jethrodesign wrote:
I would love to learn more about how to choose an InDesign working color space when you don't know the end printer (or if the end printer is clueless); how to deal with Illustrator native files that will be placed in InDesign (RGB? CMYK? Embedded profile?); how to deal with pre-existing elements that may be in the wrong CMYK color space; and possibly the option of taking color management into your own hands if the printers aren't knowledgeable; etc.
If the printer cannot provide an ICC, maybe they can state what print standard they use (GRACoL, SWOP). If you know that and the paper type, use your best judgement in selecting an ICC. Look to the IDEAlliance website, there are 2 SWOP profiles and one GRACoL profile that are good to use for coated stocks.
As far as mixing existing CMYK with RGB, opinions may be varied. Let's say you have a job, moving to Coated GRACoL 2006. You place RGB images, US Web Coated SWOP v2 CMYK images, US Web Coated SWOP v2 Illustrator, and custom GCR CMYK rich black images.
When these are placed into the GRACoL InDesign document, the default behavior is to preserve CMYK numbers. The GRACoL CMYK is assigned to all of the placed CMYK content.
Now you output a PDF with the settings you described earlier. PDF/X-4, Convert to Destination, Document CMYK (GRACoL). Even though you had US Web and GCR originally, in the PDF it is all Device CMYK (when output from ID CS4). Furthermore any user must assume that all CMYK is GRACoL, because that is the Output Intent. Also, if the GRACoL is a decent representation of the print condition, you can soft proof everything accurately in Acrobat (and InDesign for that matter).
If this PDF gets handed off to the printer, his duty is to RIP the CMYK and preserve numbers. The only number shifts will occur at the plating stage via plate calibration curves, which is not an ICC conversion.
If a CMYK - CMYK conversion is necessary, the printer must get you on the phone and let you know that he is re-converting all your CMYK content. For him to do that without informing you is, well, nuts. You've already done the conversion yourself. Every conversion is (technically) damaging,
Now assume that you output PDF/X-4 with no conversion. In that case, you have RGB and CMYK coexisting in the PDF output. Again, all CMYK should pass through the print RIP with numbers preserved. All RGB would be converted to the Output Intent already present in your PDF. If there is something wrong with that Output Intent, it's the printer's duty to get you on the phone and let you know. I say that because you, as a designer, have already soft proofed everything in the job in the GRACoL color space. If the printer wants to switch horses mid stream, he's got to let you know. (Side note – a printer taking a ownership of a special CMYK - CMYK conversion is highly unlikely. If they had a shop CMYK, they would have given it to you in the first place).
In summary – it is the print industry standard to preserve incoming CMYK numbers. If a client gives me a job full of US Web Coated SWOP v2, I can't very well treat that the same as incoming RGB and start converting to a different CMYK. CMYK is already cooked. If you re-cook it it stands to get burned. The only time CMYK-CMYK is warranted is (a) when Total Ink Limit is a factor (uncoated) or (b) the color is so far off on the proof that re-cooking only stands to help it.
What I WILL do is tell the client that they may get a better print result if they either supply RGB with no predetermined CMYK destination (I convert to press CMYK), or they use a different CMYK that more accurately describes the print condition.
Message was edited by: Printer_Rick