Is it an acceptable approach to determine paper gamma around 1D output density (say, point 11 on X) like this: g=(Y12-Y10)/(X12-X10)? What are the values of gamma for different paper grades? UPD: point numbers are from Kodak Gray Tablet #2, 21 steps, starts 0.05D, step 0.15D. Steps are on X axis, Y is resulting print densities. Point 11 was printed to produce resulting density around 1 D, points 10 to 12 are on the linear segment of the resulting characteristic curve. Sorry for being unclear, my first post.