Published on julio 15th, 2009 | by admin0
Working in a mixed-RGB-CMYK-CMYK Work Flow.
Adobe InDesign assumes – correctly – that anything in an InDesign document that is already in CMYK should not be converted to a different CMYK when printing (or making a PDF file).
This means that objects (photos, digitially-originated images, graphics generated in InDesign) that are in the CMYK color space will not be modified at all when you print to a CMYK device. Meanwhile, graphics, photos, and objects generated in InDesign in RGB, grayscale or Lab color space will be converted to the CMYK space at print time.
This week I am in the middle of a typical color project. It is a 72-page booklet, published annually, that includes legacy photos (already in CMYK) and new photos in RGB (each has an embedded RGB camera profile).
The booklet was printed in another county for many years; now it’s here. I am acting as middleman-trouble-maker, helping the designer and the printer to get the color in the job right. The designer has prepared all the pages in InDesign, and is ready to print – spare some last-minute changes in the copy, and another round of proofreading by the client organization.
This menu, found in InDesign’s PDF conversion palette, allows an operator to convert CMYK to “new” CMYK, or not (shown). In any event, other color spaces will be converted to the destination color. The «preserve numbers» option means: DO NOT CONVERT ANYTHING ALREADY IN CMYK.
The printer is doing everything right. They purchased Idealiance G7 Curve software to create neutral grays on their plates and press, and they have standardized their density settings on the press so that the pressman can bring the press to starting density literally “to the numbers.” Once the G7 neutrality was confirmed, the printer ran an IT8 color target and made an ICC profile on the exact paper that will be used for the final booklet. The profile measures nicely in ColorThink Pro. The press gamut is large; the response of the press compared to common “standards” looks very good. Everything is in place.
The printer calibrated their Macintosh display using the X-Rite iOne Pro instrument, and their viewing booth seems up-to-snuff (I will test it later with the iOne Pro to see if it’s in proper output condition).
All of this should be routine, except that the press sheet they ran yesterday does not match the screen at all, and the legacy photos (printed from previous years) don’t match the new photos (or versa vice). [We’ll work on the display-to-proof proofing again later.]
This is the work flow we are using for the initial tests. It leaves all existing CMYK unchanged, while converting all RGB (an other) color images and art into “new” CMYK using the new profile.
I brought two press sheets to the designer who said, “They are 90 percent there…” – which is very good news. The designer will, later this morning, compare the press sheet to her display where the “original” work has been done. The challenge here is to decide how to go the last ten percent.
The press is literally neutral, and really should not be used to do color balance, so the correction of the process belongs to the designer. One option is to convert the legacy CMYK to the new CMYK; I don’t like to do this because it has proven to be a bad move to convert CMYK to CMYK for print (except for gross changes like sheet-fed to newsprint), but it might come down to that. The subtlety of the differences can be characterized by the designer and the printer scratching their heads, saying, “Hmmm… ummmm,” and then, “This one is a little oranger than the one that printed last year.”
To expand a bit on the reason for my reluctance in changing legacy CMYK to “new” CMYK: the profile of the presses used in previous years is unknown to me. Was the color converted using GCR? Will converting it with GCR another time cause the image to become emaciated in the shadows? What was the Total Ink Coverage (sometimes called TAC) greater than the “new” TIC? And, if it was lower, then what will happen? (probably nothing). Will color gremlins slip into the images as they are converted from old to new CMYK? There are enough possible pitfalls here to cause me to lose sleep over this project.
But, converting the legacy CMYK to new CMYK might be the exact thing we need to do to get compliance between the previously-printed images and the new.