Definition: Chart for testing resolution ability of optical system e.g. lens, lens/film combination, scanner: various designs depending on purpose. * May consist of series of sets of lines at progressively smaller spacing or series of lines radiating from centre etc. More contrast, better figures In quoting resolution figures for lenses, we are seldom told the target-object contrast - but we should be. A lens can seem to resolve very well with high-contrast targets which are much higher contrast than normally encountered: more realistic figure would come from testing with a medium-contrast target, say, 1:32, which is already a four-stop difference - whereupon the resolution figure usually plummets.
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