I think not. The reason is that the numbers on the lenses are approximate only. Also, wide angle lenses are more likely to reveal any focus accuracy flaw. To ensure the accuracy of the viewfinder/screen, the only testing distance is infinity (AFAIK). However, the accuracy of the viewfinder is not the same as the accuracy of the film plate (because Pentax 135 SLR bodies employ washers to guide the distance between the mount and the film plane). Missing washers (not uncommon with used Pentax bodies which were serviced by non-Pentax experts) mean lenses would focus beyond infinity (more noticable with wide angle lenses). I had an used Super Program with this exact problem.My question is, if I should measure to a stake placed at 5 feet, then one at 15 feet, could I expect a linearity all the way out to 50 feet and beyond? In other words, if I took the easy way out, and did an accurate measurement only at 10 or 15 feet, and the lens agreed with that, is it rational to assume that my measurement with split image rangefinder will be good for ALL distances shorter and longer than that just verified?
regards,
Alan Chan
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