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Andrew Mehuys
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Ctein, I beleive you are a keen amateur astronomer. So you know how difficult it is to achieve focus at infinty. So difficult in fact that many astrophotographers use a method devised by french physicist Foucault which I'm sure you've heard about. In the 60's some so-called astrographs (just a lens with a film holder) were focused by trial and error. A bright star was left to trail for x seconds and then exposure was interrupted. During that interruption, a slight tweak of focus was accomplished (the lens had a micrometric scale to help in this very precise tweaking). Another exposure was then made on the same piece of film and so on. After development, the film was examined with a microscope and the thinnest star trail would determine the best (but not necessarily perfect) focus. And that was just to determine focus at infinity ! So I can't imagine any system, RF or SLR that could ever be that precise. We'll have to contend with good enough for quite a while I'm afraid.
Toggle Commented Feb 1, 2010 on Focusing Follies at The Online Photographer
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Feb 1, 2010