A recording microdensitometer is described that has a resolving power of 800 lines/mm when the scanning aperture is 1 μ wide and 200 μ long. The response is linear in density to 3.0 for the same aperture. By narrowing the aperture to 0.1 μ, the resolving power can be increased to 1800 lines/mm. The record is made either on chart paper with rectangular coordinates, on punched cards, or on both.
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Altman et al. (1956) studied this question.