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Epson R2400 inks density

A week ago I gave to a friend of mine a print of YMCK and RGB patches (Epson R2400 on Pictorico) for an analysis of their UV-VIS spectra, and now I have the results. The graphs are posted in www.albertonovo.it/scan/epson_inks.html
What can be seen is that in the 320-400 nm region (UVA), the yellow ink absorbance abruptly falls from about 3.6 at 400 nm to its minimum at about 440 nm (A=1.5).
The other inks have a neatly different behaviour, with an absorbance rising when going from 400 to 320 nm. The most dramatic change happens with magenta and cyan, which have an absorbance of about 0.75 @ 400 nm and respectively 3.2 and 3 @ 420 nm.
The absorbance values of red, green and blue are not simply the sum of the primary (CMY) colors at a given wavelength, but can be roughly approximated if the sum is multiplied by 2/3 (see for example the curves of C, B and G, the last two being C+M and C+Y, in the 600-750 nm region).
Moreover, the absorption of 50% saturated color patches (i.e. R=255, G=255, B=128 for a 50% Y), that one likely thinks they should have 50% absorption of the full strength ones, are three or four times lower (not shown in the graphs).