CHROMiX

curves to help evaluate profile builds

I’m entering the daunting work of 6 channel setups and profiles in my RIP, with an Epson 9900. Using ColorThink Pro to help the work and aid in finding ideal setups that may result in better profiles, I’ve always checked out the curves. The RIP I use allows “dot gain”, a bit of a misnomer, to be set by the user per channel after linearization. what it really is is individual gamma output setting. I’ve found particular settings that consistently result in smoother results in the ColorThink curves display, and they are not equal per channel.
Since upgrading to Pro, I now see the dot gain display as well, which of course reveals my slightly different per channel output.
Sorry for the long intro, my question is this- Is there a theoretical “ideal” ColorThnk will aid me to work towards? I realize the curves are showing me the neutral build, and may not reveal much about the immense number of other colors may perform in the profile. Does hitting approximately equal CMY curves in the neutral build really indicate a desirable goal? Then the individual CMY dot gain amounts are different, which may effect more of how each ink performs differently down saturated primary grads- is there a desirable target there as well, and are these two issues at odds as they seem?
Additionally (whew!), as we all know, the vast majority of transforms and colors in art are far from either neutral axis grads or saturated grads, and in fact are more complex ink combinations transitioning into other complex builds in ways unrelated to the above simpler transitions, so how can these tools aid me in building more ideal profiles for general real world work, or do they represent more diagnostic aids when things are obviously off?
Thanks,
Tyler

Hi Tyler…OK, I’ll bite. :slight_smile:

I’ve done a bit of work exploring different linearization methods so maybe I can offer an opinion.

First off, contrary to some folk’s opinion, I don’t think linearizing for gray balance is particularly useful for an inkjet printer. If the result of “linear” gray balance where C=M=Y is very non-linear with respect to the primary and secondary ink channels, then I think it’s a bad thing.

I tend to think in terms of linearizing in such a way that the result is very even distribution of “tones” in 3D Lab* with respect to primary and secondary inks. Looking at both an a*/b* chroma plot and the L* axis, you want a more-or-less even distribution.

You can think of this as a sort of “Delta E” linearization where each step of ink on a step wedge results in equadistant dE values from 0-100%. IOW, if the dE difference between 0% and 100% is, say, 20…then the dE at 50% would be 10. Make sense?

I’ve used this method enough times (using a spreadsheet I put together) that there is at least “trends” in what this looks like in terms of “dot gain”. With K ink for example, because it is primarily about L* distribution as opposed to chroma, the result is almost always 27% TVI, +/-2%. The other inks tend to vary between 14% and 23% depending on the primary with magenta typically being the lowest TVI, cyan in the middle and yellow being the highest at around 23-25% TVI.

Something to think about is that, K being primarily about L*, you should linearize using even L* distribution as your goal. Yellow on the other hand has very little L* variation but huge chroma (b*) variation…so it should be linearized based primarily on chroma distribution. Magenta and cyan need a combination of L* and chroma distribution since they are dominated by neither L* nor chroma.

Again, I’m oversimplifying a bit but dE distribution is a good start to thinking the correct way in terms of what “linearization” should mean. ColorThinkPro is a HUGE help in visualizing this…while I was developing the formulas in my spreadsheet, I was constantly relying on CTPro’s 2D and 3D Lab plots to help me visualize exactly what was happening…CTPro was invaluable.

Terry

Terry, this is an astonishing amount of hard work and information to share, thank you. I have some work to do to make the most of it, but in my pea brain simplified version- it never made sense to me that neutral axis gray balance should necessarily be comprised of equal CMY, because that assumes a perfectly neutral K ink, which rarely occurs, particularly with Epsons. Therefore, equal CMY down the middle has to be achieved with less than ideal builds and transitions in other areas of the total space… would that be correct?

So then the questions are, what is ideal, which you have provided much about, and then how to implement… which becomes my task on my setups.
Thanks again,
Tyler