I1Profiler v Profile Maker 5. The part that matters most to photographers.

[Doug Gray]

In my previous post I was only looking at the differences between the two regarding in-gamut printing. While this is most critical to people that need precision printing of images that are already within the printer's gamut most photograph printing involves significant colors outside the printer gamut.  Visually, the two perform virtually identically for in-gamut colors using RelCol Intent.  However, there are major differences in how the two deal with colors that are out of gamut and this will significantly alter the appearance of prints. This thread will explore these differences. I am in the process of measuring this now with results forthcoming. Should be interesting.

[Doug Gray]

First I examined the overlap of sRGB and Adobe RGB with the printer's gamut. While it's well known and discussed that glossy prints on a good photoprinter significantly exceeds sRGB and even Adobe RGB, less well known is that there are also large amounts of colors in sRGB and Adobe RGB that exceed the print gamut. Tested were a Canon 9500 II using Epson Ultra Premium Glossy. This has a high color gamut typical of glossy prints.

I selected a very large set of RGB values, all combinations of RGB triplets containing 0 to 255 in steps of 5 in ProPhoto RGB as this encompasses the entire printer gamut as well as the lesser RGB gamuts. From this I established an in gamut set consisting of all printable colors that were no more than 2 dE2k off. Then, I made a union and intersection of these printable colors with the sRGB and Adobe RGB gamuts. First the portion of the gamut that can't be printed in sRGB.

Percent of printer gamut outside sRGB: 18%
Largest printable color Lab: 50.2, -65.6, -30.9   sRGB Lab:  55.1, -26.9, -22.9  dE2k:13.6


In other words, 18% of the printable colors couldn't be printed when constrained to using sRGB. The printable color, as expected, that was furthest from the sRGB space is an intense cyan.

Similarly for Adobe RGB

Percent of printer gamut outside Adobe RGB:  4%
Largest printable color Lab: 48.2, -53.2, -41.2   sRGB Lab:  50.4, -35.5, -37.6  dE2k: 6.2


Here we see the printable color most outside Adobe RGB is also an intense cyan but over half the dE2k is recovered. Further, the portion of the printer's gamut that is outside the Adobe RGB space has shrunk to 4%.  Ok, nothing really new here.


However, the flip side is to look at colors that are within sRGB and/or Adobe RGB that can't be printed. This isn't usually looked at but is sometimes a fairly large effect. The main causes are that RGB spaces are based on emissive sources and are capable of pretty bright colors at the RGB triangle corners which are the points of highest saturation in a RGB color space. They can also represent very colors all the way to their gamut triangle. Printers can't print highly saturated dark colors. The following examines the unprintable colors in each space and the way I1Profiler and Profile Maker 5 map these unprintable colors into ones that are printable.

For these tests we define "unprintable colors as those that are more than a dE2k of 2.0 from the requested color.
First, let's look at sRGB:

I1Profiler Results for sRGB
Percent of sRGB colors that exceed the printer gamut: 27%
Average dE2k of out of gamut colors  5.1
Max dE2k of out of gamut colors 11.4
Max dE2k - Req Lab: 34.2, 71.0,-104.2,    Prnted Lab: 29.4, 30.0,-62.9, dE2k: 11.4

Profile Maker 5 Results for sRGB
Percent of sRGB colors that exceed the printer gamut: 27%
Average dE2k of out of gamut colors  6.0
Max dE2k of out of gamut colors 16.1
Max dE2k - Req Lab: 35.2, 71.7,-102.4,    Prnted Lab: 30.9, 20.5,-65.3, dE2k: 16.1

Here we see that about a fourth of the sRGB colors aren't printable. There were 50% more unprintable colors in sRGB than printable colors outside sRGB. Also, I1Profiler does a better job of mapping these out of gamut colors with a smaller dE2k than does Profile Maker 5. The color that suffers most is a fairly low luminance but high saturation magenta.

Ok, now let's look at Adobe RGB:

I1 Profiler Results for Adobe RGB
Percent of aRGB colors that exceed the printer gamut: 43%
Average dE2k of out of gamut colors  5.6
Max dE2k of out of gamut colors 15.3
Max dE2k - Req Lab: 83.2,-129.1, 87.2,    Prnted Lab: 66.4,-77.9, 56.0, dE2k: 15.3

Profile Maker Results for Adobe RGB
Percent of aRGB colors that exceed the printer gamut: 43%
Average dE2k of out of gamut colors  6.3
Max dE2k of out of gamut colors 16.7
Max dE2k - Req Lab: 36.9, 73.3,-102.3,    Prnted Lab: 32.1, 20.5,-64.9, dE2k: 16.7


With Adobe RGB we are up to 43% of the colors that can't be printed. Further, there were 10 times more unprintable Adobe RGB colors than printable colors that are outside the Adobe RGB space.  However, the average and max dE2k values are only slightly higher than for the sRGB space. It seems likely that the capture of additional printable colors in Adobe RGB has somewhat offset the increase other, unprintable colors. Another factor is that as the gamut expands to more saturated colors the dE2k compresses relative to the conventional dE76.

And now for ProPhoto. Here, we are entirely outside the printer gamut and, since many of the colors in ProPhoto are theoretical and can't actually exist, the meanings of the dE2k are, at best, just an indication of color difference.

I1 Profiler Results for ProPhoto RGB
Percent of ProPhoto colors that exceed the printer gamut: 73%
Average dE2k of out of gamut colors  8.8
Max dE2k of out of gamut colors 22.5
Max dE2k - Req Lab: 87.6,-186.7,151.0,    Prnted Lab: 66.7,-71.7, 64.3, dE2k: 22.5

Profile Maker 5 Results for ProPhoto RGB
Percent of ProPhoto colors that exceed the printer gamut: 73%
Average dE2k of out of gamut colors  9.3
Max dE2k of out of gamut colors 23.9
Max dE2k - Req Lab:  1.6, 63.1,-129.1,    Prnted Lab: 31.1,  6.1,-61.3, dE2k: 23.9


Three quarters of the ProPhoto RGB space cannot be printed. OTOH, many of these don't exist. Further the ICC PCS space clips Lab a and b colors at -128 and +127.

In conclusion, there is clear benefit to soft proofing. The effects of out of print gamut colors in the sRGB space can be controlled because most profiled monitors can do a good enough job of showing what can actually be printed as opposed to displayed and it is not only significant but is a larger factor than the printable colors given up by use of sRGB.

This is even more true when using Adobe RGB as a working space.. Only a small number of printable colors are given up but quite a large percentage of Adobe RGB is not printable. Soft proofing with a high gamut monitor should be considered essential when using Adobe RGB or ProPhoto RGB.

There are some differences between I1Profiler and Profile Maker 5. While I1Profiler maps colors more closely than Profile Maker 5 the differences aren't all that large and this particular test only explores the dE2k closeness. A much more important factor when mapping out of gamut colors is how the hue, saturation, and luminance is mapped. Particularly how smoothly they are mapped over gradients. This is more a question of preference and not numbers.