I recently purchased a Kowa 210mm process lens and am working at finding a way to put it into a shutter. From info that I have received here the elements should fit a Copal 1 making the lens a F6.8 rather than F9. My question is: I have found a Polaroid Copal 1 shutter, assuming that the elements do in fact fit, how do I go about converting the aperture sizes/scale to work with the longer lens? More simply stated, is the measured opening size for an aperture constant with focal length (i.e. F5.6 is F5.6 no matter what the length of the lens) or are their sizes related/proportional to lens length? If they are proprtional to lens length is there a table (or formula) of aperture sizes somewhere that I can use to create my aperture scale? Thanks for the help...
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