Archived posting to the Leica Users Group, 2000/11/01
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]This is a quote I saved from one of Jim's posts a month or so ago: "With each pixel, in a good, high quality sensor, averaging 5x5 microns, this is 25 square microns for one 8, 10, or 12 bit pixel. 1024 shades from white to black. A grain in a fine grain film emulsion averages 1x1 micron (one micron square) and contains 20 billion silver halide molecules. Somewhat more density possibilities than 1024, in 1/25th the space." This indicates that in order for a digital sensor to provide the equivalent of a fine grain film (not taking into account the pseudo random size and positional nature of film grains), the digital sensor would have to be 25 times the physical size of that film, in order to capture the "equivalent" information that film captured. To extrapolate the 1 micron film grain size to "equivalent" DPI, that would mean a fine grain film has an "equivalent" DPI of 25,400 DPI. 25.4mm/inch divided by .001 microns/mm... This is just meant to show the arithmetic...not to claim that one needs to have that kind of resolution to make a useful image... Any idea what the grain size is of, say, Tri-X?