On Fri, January 21, 2011 09:53, ADavidhazy wrote: > Agreed ... factors of 2 are easy but what if you wanted a factor of 4 > or 6 or 75? > I will agree again that is is academic but in certain obscure and > unanticipated applications it might be useful to know this if you want > to determine a specific > f number rather than just guessing at it. The question was asked in an > academic > setting - part of the overall technical education of photo technology > students. You have an entirely legitimate interest in the academic side of this! I have to agree. (Mine is perhaps not so legitimate, except that any hobby that doesn't harm others seems legitimate enough to me.) And there ARE things people want to photograph, either scientific experiments or rare events, where the mainstream "test-and-chimp" approach to getting the correct exposure actually isn't feasible. For the vast majority of photos, that pragmatic approach works well (and, when possible, I would insist on testing any result I calculated before relying on it). If one of the things you know is "this produces 68.7 times as much light as that thing I tested", you end up with exactly the question you are asking here. > PS: Interestingly ... most students here don't know what a > photographic enlarger > is or what a light meter is either! The digital age is upon us! ;) <- > wink! The light meter was a primitive form of the digital camera, with very low resolution :-) . -- David Dyer-Bennet, dd-b@xxxxxxxx; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info
