CompuServe Messages

#Printing

    13-Apr-94 11:34:06
Sb: #Printing
Fm: Marion K. Marks 70700,2777
To: Steven Elliott 70303,1363
It occurs to me that since we're talking about a real continuous-tone printer here (assuming one is using the dye-sub/photo-realistic kit), that we can actually do accurate gamma calibration the "standard" way: namely, generating a document with swatches of RGB 128/128/128 gray juxtaposed with swatches of black & white checkerboards at single-pixel resolution (just like the Adjust Gamma dialog in 3DSr3 itself!). I propose making a page that has such swatches in gray, red, green, blue, magenta, yellow, and cyan, going all the way down the page. Gamma-adjust the page in strips of various values, starting with 0.5 at the top and going down to 2.5 at the bottom, in 0.1 increments. Then print, and see what comes closest for each of the primaries (remember, primaries for a printer are CMY, not RGB!), and narrow it down accordingly, perhaps by re-gamming the strips in the ranges found down to 0.005 increments, until precise gamma is found for each of the primaries and overall. Theoretically, this should take at most two prints: one of the "coarse" gamma strips (0.5 to 2.5 in .1 increments), and one of the final zoom-in (pick the two closest values from the coarse and use them as the limits, with intermediate strips in increments of 0.005 or some such).