Focusing Criterion for Ground-Glass-Focused Lenses, Derived from MTF Measurements.
Lenses used in the graphic arts and in professional photography generally are focused on a ground-glass screen. In order to obtain a mathematically defined focusing criterion, a sector star target was visually focused on a ground glass through several of these lenses and the MTF curves measured at various receiving planes. It was found that in the frequency range between 15 cycles/mm and 30 cycles/mm the visual receiving plane gives higher MTF values than in any other plane. The corresponding contrast values were found to lie between 0.3 and 0.5.
Kuttner
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