My method in linearizing with QTR is, I understand it, consistent with what others do. My procedure, basically is to print step wedge targets in the Gray Gama 2.2 color space with Print Tool using No Color Management. I have gotten very good results in practice by linearizing with these targets, using both the Measure Tool with ProfileMaker 5 and iProfiler.
There was in interesting discussion yesterday on the carbon forum in this thread,
https://groups.yahoo.com/neo/groups/CarbronTransfer/conversations/topics/8930?reverse=1
Some of the discussion seemed to conflict with my procedures so I asked Calvin for permission to use his comments on this forum, and I attach them directly as he stated, his words in italics. Thanks in advance for comments.
Message One from Calvin
Looking at the Eye-One-Readme text, Roy explains the linearization process with the 21 step tablet he provides. The problem is he is linearizing a file in the Dot gain 20 profile space with lab values. In the end he shows an ideal linearization and has an L value of 57 for his 50% patch, when the L value should be 65. Following your book, it looks like this is how you are doing it as well. This would explain why yours and Peter's print is coming out too dark. If one is going to linearize with L values directly, then don't print a test chart with patches calibrated to the profile spaces of dot grain 20 or gray gamma 2.2. Make a test chart with the values corresponding to L values.
Message Two from Calvin
So let me get this correct, you are printing a test chart in gray gamma 2.2 then reading the patches and calibrating to evenly space or linearize the L values? If this is what you are doing, your print is going to come out dark. L values are not evenly spaced in either dot gain 20 or gray gamma 2.2. If you try to evenly space or linearize the L values for a test chart in either profile, the calibration will be wrong. For example the L value for a 50% patch in gray gamma 2.2 is not 50, if you were to have a perfectly white paper and pure black, but rather 54. The 90% patch is not 20, but rather 6 and so on. The difference in dot gain 20 is even greater. The 50% patch has an L value of 62. Let's look at a real world example of calibration- L values for paper white might be 95 and black might be 10. If you take a test chart in dot gain 20 and read the 50% patch, it should read 61 which is not the midpoint between 95 and 10. The midpoint is 52.5. The difference being 8.5, so your print would come out 8.5% too dark.