CHROMiX

RGB GRACoL color bar

I would like to create a RGB version of the new IDEAlliance CMYK Color Control Strip. I would use this rgb image on proofs I make that get sent to a commercial printer, to verify that the proofs are made to GRACol standards. I currently send Adobe RGB98 tagged images thru a Colorburst rip that simulates GRACoL.
Any ideas how I could create such an RGB Control Strip or is there any other RGB image I could put on my proofs to verify the RGB to GRACoL conversion is GRACoL compliant??
The rip is a bundled version that dosen’t allow me to gang images “on the fly”, so I end up ganging all my rgb images in Photoshop to fill up the sheet.
Would a ICC profile conversion converting the IDEAlliance CMYK Control Stripf using the"official"GRACoL profile as source profile to Adobe RGB give me reliable results and if so , which rendering intent would I use.
I’m currently using Profilemakers Measure tool to read CMYK proofs that I make with the IDEAlliance Control Strip on and am looking for some similar Control for my RGB workflow.

I don’t think your plan will work. Color bars (including the one you are talking about) are used to measure how a particular CMYK color combination will be rendered by your proofing device or press. The whole point is that it contains known CMYK values, which should produce known LAB values when proofed (or printed) to say GRACoL Coated1. By colorimetrically measuring the output, anyone can verify that the proof is in compliance.

The reason your plan won’t work is that your RIP is going to convert the RGB values to CMYK and no matter how good your CMM, it is highly unlikely that it will convert them back to the same exact values that were in the color bar originally, especially your pure (C,M,Y, K) values.

Are you actually releasing RGB images to commercial printers? When you send data to your Colorburst RIP, do you have all color management off in Photoshop so that the RIP is doing the conversion? There must be settings on the RIP which tell you what source profile it is expecting for RGB, what destination profile it is using for CMYK and what rendering intent it is using. You can test your RGB workflow by converting your images in Photoshop using the same settings as your RIP, then output through your CMYK workflow (with color bar). Do the images look the same? Is the color bar in compliance with GRACoL? If so, your in RIP conversion is OK.

Good luck!
-Todd Shirley

If you have Quark or InDesign you could have the best of both worlds and send your RGB data to the printer along with the CMYK proofing bars.