Method of scanning photographic film images using selectively determined system response gain calibration

摘要

Gain factors for correcting pixel to pixel variations in system response in a multi-pixel scanner array are determined by calculating gain factors for a so-called "open gate" condition (with no film present), by calculating gain factors for a so-called "Dmin" condition (looking at the minimum density of the film), and by selectively combining the "open gate" gains and "Dmin" gains to create composite set of gain factors which overcome the shortcomings of using either original set of gains alone. The composite gain factors can be a proportional sum of the two original sets of gains with the proportionality changing on a pixel-by-pixel basis to select more of one set of gains or the other set of gains. A number of discriminating functions are disclosed which may be used to calculate the proportionality based on some understanding of how the presence of film changes the characteristics of the scanning system.