Yeah it's hard to judge under the microscope too on the depth. Normally I don't look under my work microscope because the lighting is really hard to manage so I usually use a 45x lighted loupe. Under the loupe as I progress up the grits I always see a finer scratch patter with each grit level and almost a mirror reflection under the loupe at 8k until I get to the 16k. then the edge looks "scratchier" and less mirror like than the 8k. An so is my fear that my 16k is polishing less than the 8k. Because of this I decided to get the higher powered microscope out in hope to see what is going on.