In article <1993Apr6.011605.909@cis.uab.edu> sloan@cis.uab.edu (Kenneth Sloan) writes: >Why didn't you create 8 grey-level images, and display them for >1,2,4,8,16,32,64,128... time slices? By '8 grey level images' you mean 8 items of 1bit images? It does work(!), but it doesn't work if you have more than 1bit in your screen and if the screen intensity is non-linear. With 2 bit per pixel; there could be 1*c_1 + 4*c_2 timing, this gives 16 levels, but they are linear if screen intensity is linear. With 1*c_1 + 2*c_2 it works, but we have to find the best compinations -- there's 10 levels, but 16 choises; best 10 must be chosen. Different compinations for the same level, varies a bit, but the levels keeps their order. Readers should verify what I wrote... :-) Juhana Kouhia