Response to Density step tablets (calibrate a scanner to be a densitometer)

Ryuji, You should revisit semi-log and log-log graph paper. It really is a big help when you are seeking a curve to fit data. If you scan a step density tablet and the numbers obtained from PhotoShop level adjust with preview shut off plot on semi-log paper as a straight line, you have a pretty good idea about what kind of erquation will fit. If you want to skip the equation, all you need do is scan your negative, use the same level adjust function to read salient points from the neg, and then read density values from the graph. You can apply the same procedure to read reflection density from prints by scanning a reflective gray scale and plotting the level values of the steps. Of course, you do not really need to use semi-log paper, but it does help to stretch out the increments between low density steps.

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