Really, this is a note to remind me that, based on my empirical testing, for low values of gamma, the gamma value at the scanner and the gamma value in GIMP are additive, and sum to about 3.2. (This puts Zone 5 at a digital (linear) value of 127 out of 255.
There's probably a mathematical proof of this, but I'm not going to try to derive the result. Suffice it to say that I will now start using scans with a gamma of root 2 and then add 1.8 in GIMP. This is just a mnemonic device; root 2 is common and 1.8 is the typical display gamma.
Neither value has any substantive significance here. However, given the odd things the Epson software does with the tone curve and the top and the tow, I decided not ti use a gamma over 1.5 at the scanner. I also don't want to have GIMP to all the rescaling since I think this is best done at nearest the source in the hope that it's achieved in the AD converter, and not afterwards.
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