In response to the comments above about improvements after optimizing profiles in i1Profiler, I attempted my own investigations.Introduction
There has been some discussions going on the luminous-landscape and other forums about optimizing profiles in i1Profiler. The general view is that if one starts out with a large number of patches for building the initial profile, say around 2000 patches, then the optimization routine does not show much fruit. This is true for when the optimizing patches are generated automatically by the “Smart patch generator”. Andrew Rodney noted that the maximum differences were less than 1 deltaE.
That is hardly any difference. However, Andrew and others have seen a marked increase in gray neutrality and smoothness when using the 2502 spot grays optimization file and process detailed here: http://www.i1upgrades.com/2011/08/how-to-use-the-tc-2502-gray-optimization-chart/
I want to test whether optimizing a profile with patches generated by the smart patch generator result in any improvement. I also want to test whether optimizing with the custom 2502 spot grays will result in any improvement. I tested this on two profiles, which I will call "Profile A" and "Profile B" for simplicity.
Both profiles were built from targets containing over 3000 patches, but less than 4000 patches. Both targets contained a significant number of neutrals, more than 329 neutrals and near-neutrals, which is the maximum number that i1Profiler can generate automatically.Test ResultsOptimizing Profile A with 2502 grays
• After optimization, grays became noticably cooler, especially in the highlights. Smoothness was slightly but visibly improved.
• There was a maximum increase of 5 values in the blue channel (the maximum increase occurred from RGB114 to 122), and a max value of only 4 in the R or G channels. This explains the cooler grays.
• There was also slightly improved separation in the dark grays, close to black, in the RGB 0 to 60 range)
• After optimization, there was a noticeable but slight increase in separation in the blues near clipping (Blues 235 to 255).
• After optimization, there was huge separation loss in the yellows near clipping (Yellows 240 to 250)Optimizing the Profile B with 1260 patches generated by the “Smart patch generator”
I generated a 1260 patch chart using the “Smart patch generator”, which happen to contain a number of colors and a fair proportion of neutrals and near-neutrals, in a ratio of about 2 part colors, 1 part neutrals.
The optimized profile has a gamut volume of 766 217, calculated by ColorThink Pro.
The original profile has a gamut volume of 768 465, calculated by ColorThink Pro.
• Gray values hardly changed. A maximum increase of 2 values in the blue channel and a maximum change of only 1 value in the R or G channels was noted.
• Grays did not seem to get lighter or darker.
• Grayscale did not become smoother.
• Magentas were the most severely affected. It appears that i1Profiler attempted to correct the magentas to give a smoother result, but a large portion of it was lightened, and a small but visible transition to the darker shades appeared. This is arguably a worse result.
• Dark Oranges and greens appear to be slightly smoother, but the difference is so slight I can barely make it out in the softproof. Only by converting a granger rainbow to the original and optimized profiles and comparing them as two layers in a non-color managed Photoshop document using the difference blend mode, did I first notice this difference.
• There was huge separation loss of the yellows near clipping (Yellows 235 to 255) after optimization.
• Blue separation was very good to begin with, so optimization did nothing to improve it.Optimizing Profile B with 2502 grays
Optimization failed. X-rite said that there was an error creating profile, despite me making 4 different measurement scans, and multiples tries rebooting the computer, and re-launching i1Profiler. I suspect that the memory limit on i1Profiler was reached, because of too many patches in total (3256+2502 patches). I get the same error after I have asked i1Profiler to generate about 8 large-patch profiles, and I have to re-launch the application to clear the memory.Preliminary Conclusions
The Profile B did contain a fair bit more spot gray patches than Profile A. This resulted in a profile, which before optimization, that is already far smoother than any of the i1Profiler-automatically-generated-patches-based profiles I have created, and is even smoother than Profile A after optimization with 2502 grays
. This is outstanding performance.
It seems, to my way of thinking, that selecting optimal patches for profiling does result in a superior final profile, and having a superior profile is better than trying to optimize a sub-optimal profile. More on optimal printer targets later.
I wish to make it clear that Profile A already has a pretty smooth grayscale gradient with almost no banding to begin with, and it is as smooth as the i1Profiler 5837 patch profile. The additional smoothness I see from either the optimization process or the superior custom target is subtle, but visible
This investigation also informs me that the optimization that i1Profiler does is detrimental to the separation of high saturation yellows, a color which I find for my Canon iPF8100, is very hard to separate to begin with. I am also not happy with the way it dealt with the magentas.
Getting a smoother grayscale with Profile B took far less time, ink and paper, and produced a smoother grayscale than Profile A after optimization.
All in all, I have to say that an optimized version of an already very good printer profile, is worse than the original profile.
An optimized version of a suboptimal profile probably will result in an improvement, but I do not think creating a suboptimal profile to begin with is a good idea. I also question whether the gains of optimization, at the cost of additional ink, paper and time, is worth it.