Re: [ECI-EN] Things about color management that are not clear

Hello Peter, A few days ago, you answered some of my questions very kindly ! I still struggle with something however. You wrote to me (and I experimented a bit so I have seen it first hand) that if you convert to destination with "preserve number", then the original separation stays the same. If I understand correctly, the numbers of the coulours before exporting the document and after are still the same ? If it is the case, what is the difference between "no conversion" and "convert to destination (preserve numbers)" ? Also I wondered if I set up "ISO coated v2 ECI" as working space when creating a document (the intent is to print on coated paper), should I use "Convert to destination", "Convert to destination (Preserve numbers)" or "No conversion" when exporting the PDF ? It still not clear :-) I hope you can help me somehow :-) Thank you anyways ! Kind regards, Thibaut SIMONART IMPRITEX SA Avenue Vésale, 10 B-1300 Wavre Tel direct : +32 10 23 88 83 -----Message d'origine----- From: Nagy Péter Sent: Friday, December 09, 2011 1:22 PM To: eci-en(a)lists.callassoftware.com Subject: Re: [ECI-EN] Things about color management that are not clear Hi Thibaut, a lot of questions, which might be answered best at a thorough local training at your site, as Jan-Peter said. Without knowing your specific problems, some guidelines: 1. OutputIntent in PDF/X is to communicate the intented color representation of the graphics. You might print to some very different papers, which can't be simulated (or even unknown) to the submitters of your graphics files. So it's easier for all of you to acquire data in a standardised color space (eg.: ISO Coated v2, aka FOGRA 39), which is well known now for of the graphics artists. 2. In your in-house production workflow you might use PDF/X and OutputIntents, but at your level it's not really necessary, because you always know the output color space (which is defined by the material you're printing on, the used inks and other process parameters). So a good practice would be to specify FOGRA 39 / ISO Coated v2 as the submission color space for your clients, but work in Illustrator in your final printing color space. You may mess around with OutputIntents if you have a lot of various materials to print on (and you have their ICC color profiles), or if you have a large staff and a sophisticated workflow. Otherwise the best would be to define each job's color space in a job ticket right at the start, and use that info throughout the production, and leave PDF/X alone, at least in-house. 3. Working in your specific, job-based CMYK color space is a must in the packaging industry. This helps you avoid most of the problems which may arise at the time of printing, and of course helps you softproof your jobs in CS application (provided you assigned the correct ICC profile to the document). 4. The difference between 'Convert to Destination' and 'Convert to Destination (Preserve Numbers)' is that the former mode always convert colors if they differ from the chosen output color space, while the latter doesn't. Example: you placed an image to InDesign, which has the color profile "SWOP v2" embedded. You output the design to PDF and choose the destination to be ISO Coated v2. "Convert to destination" will re-separate the image from SWOP v2 to ISO Coated v2 during the process, but the 'Preserve Numbers' will not: it will retain the exact separation of the original image. What's the catch? If you get images in a wrong color space, you might think that all of them must be converted. Alas, CS applications perform an ICC-based conversion, which means the black separation data will be lost – all the black type (and black-only elements) will go CMYK, they will be present in all separations. This is a disaster in most cases. 5. Sorry to say, the behavior of the 'Convert to Destination (Preserve Numbers)' option is somewhat different in CS applications and versions. That means CS2 Indesign may produce a different PDF than say CS3 Illustrator with that option choosen. This is why I suggest you to leave the conversion in InDesign or Illustrator alone, and use the 'Don't convert' option (of course this way you have to be sure that all placed graphic is in your output color space). 6. How to handle overinking, and different color spaces? The solution to that is to manually re-purpose, re-separate all incoming graphics with some very clever approach in Photoshop, or to use a device-link conversion engine, which can put the graphic to a different color space, while retaining the black separation. 7. PDF/X-4 is very important to you, as a properly authored file can contain the source data in a very abstract form. That means your task in Illustrator is much easier (the images are intact, all the graphic elements are intact and movable, there's no flattening applied, which might ruin the editability). I would say that the best for you would be to specify PDF/X-4 with OutputIntent: ISO Coated v2 as your preferred incoming data format. Kind regards, Peter Nagy Colorcom Media Budapest, Hungary _______________________________________________ ECI-EN mailing list ECI-EN(a)lists.callassoftware.com http://lists.callassoftware.com/mailman/listinfo/eci-en