Having recently acquired an Eye-One i0 ( and now its working quite well thanks to this forum), I'm interested in trying to understand a little more in depth some things I've run across as I try to build profiles.
Specifically, in Bill Atkinsons FAQ he states the measurement data can be "evaluated, averaged, selected and cleaned up before making profiles".
I'll admit I'm getting some great profiles, but my curiousity has gotten the better of me. How do I "evaluate" the raw data? How do I clean it up? Does averaging several readings as he does smooth the data sufficiently to warrant the additional effort?
If anyone can point me the in direction of a book or website that offers some insight into this area, it would be much appreciated.
You can evaluate the raw data in a few ways. One way is to perform a plot using a tool like ColorThink and see where the data points lie. They should be fairly regular. Then there are some basic sanity checks, e.g., no inversions along the gray axis. Let's say you're doing 4096 patches: the 16 x 16 x 16 regular grid. Well, if patch RGB = (0,0,0) is lighter than patch RGB = (17, 17, 17), then there's something bad going on -- usually a problem with the driver setup.
One can do multiple measurements, average the data, and check each measurement against the average to catch outliers -- measurement errors, if you will.
If you look at Bill Atkinson's FAQ, you'll notice that for his "premium profiles" he prints each target multiple times, in different orientations. At first I didn't understand why. Then I did some tests myself and found out. At least with Epson printers, the ink laydown isn't uniform across the sheet, edge to edge (even when one is printing in normal mode, not borderless mode). For example, I printed a row of 20 black patches from left to right across a sheet. 18 of the black patches measured nearly identically. The 2 located closest to the left edge of the sheet measured significantly lighter. I repeated the test multiple times and found the same thing: density isn't uniform across the sheet. Hence Bill's method of printing multiple targets, oriented differently, and averaging the results.