CHROMiX

Setting Ink Limit when making Profile

I am making 6 colour hexachrome profiles for my Roland FJ-540, using Profilemaker 5. I am having trouble determining ink limits when using canvas and semigloss paper. Documentation suggests that I should use the media.ps file supplied with Roland Colorip, but this only seems to support CMYK profiles. My question is: Are there charts to determine ink limits using six colour printers like mine? Advice would be much appreciated.

At the risk of sounding like a commercial, or self-promotional…
ColorThink Pro has the unique ability to visually determine ink limits using the ‘Constrain Channels’ feature. An ideal situation is when you have a proofer (like an inkjet printer with a wider gamut) trying to simulate another ‘smaller’ gamut device like a press. It’s a function of the Grapher while in 2D or 3D mode (although 3D is more effective). You can adjust the ink limits by adjusting a simple slider for each channel while visually making sure your proofer encompasses the simulated device. The sliders give you control over each channel associated with RGB, CMYK and MULTICOLOR devices. The resultant values can then be entered into the RIP. This method is simple and would literally take most of the mystery out of this otherwise complicated procedure. Of course it means buying a copy of ColorThink Pro…


oRick Hatmaker, CHROMiX


Rick,

Please explain this procedure in more detail - Take the reader through a hypothetical example.

Thanks.

This is rather hard to do verbally, because the ColorThink Pro Grapher tool is very visual. But I will try.
First, hopefully you are familiar with how ColorThink displays profiles in 3D mode. If not, you can download a demo at <http://www.chromix.com/ColorThink/download.cxsa?pid=10449>Assume you have CMYK Press profile and a Hexachrome Printer profile.In 3D mode, the CMYK Press gamut will be surrounded by the Hexachrome gamut (which is presumably larger). In this situation, the Hexachrome profile is shaded at about 70% opacity so that you can see the smaller and darker press profile inside.
Second, while high-lighting the Hexachrome profile in the Plot Items panel, you would select the ‘Constrain Channels’ check box at the bottom of the Plot Items panel. After doing this, another panel pops up and has individual sliders ranging from 0 to 100 for each CMYKOG channel.
Third, you simply adjust each slider (or plug in a specific value from 1 to 100) and visually try to ‘hug’ the smaller press gamut outer boundary with that of the Hexachrome gamut outer boundary. You probably want to leave a little room for cushion between the two (to allow for minor errors in the printer, ink, paper or RIP). Once you’re satisfied with the result visually, the resultant values of each CMYKOG slider can then be simply plugged into the channels controls of your RIP.

Short of a live presentation (or your own experimentation within a full version of ColorThink Pro) that’s all I can illustrate conceptually for now. It works very well under most circumstances and even dummies like me can do this.

Hope that helps,


oRick Hatmaker, CHROMiX


All right, Rick, I think I understand your method and its intent.

It appears that one has to begin with two profiles - the “press” profile and the “proofer” profile. Then, ColorThink is used to determine the ink limits necessary to create a gamut match between the proofer and the press.

I assume that once the ink limits have been adjusted in the RIP, then the output profile has te be re-made (print testchart, etc.).

If I understand you correctly, the method you described is relevant for proofing-for-press, but not useful for determining optimum ink limits prior to profiling for maximum printer color gamut.

So, based on my understanding of your response, can you describe a method for using ColorThink to determine the optimum maximum per-channel ink limit for the best possible output profile color gamut?

This is actually a trick question. — Every RIP employs different degrees of and methods for ink limiting.

Are you sure ColorRip supports TRUE 6-channel profiles?
ColorChoice does not support them. It uses CMYK profiles with a boat-load of secret sauce.