Pieter J. Roelofse |
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Flash Guide Numbers and Exposure
Hi again,
About flash guide numbers: I have a manual camera and manual focus lenses and a manual flash unit. I know how to do the calculations f-stop = GN (iso 100)/flash distance. How does this change when you use, for example, a 135mm lens instead of a 50 mm lens. Not sure about this... thanks.
August 22, 2003
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Jon Close |
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That's the beauty of f-numbers. You don't have to take the lens focal length into consideration. f/4 is the same amount of light on the film, regardless of the lens used. The only thing that will come into play is the maximum angle of coverage that the flash can provide. Depending on the model it could cover the field of view of a 35mm, 28mm, 24mm, or 18mm lens. Whichever it is, you don't want to use a wider angle lens than what the flash can cover.
August 22, 2003
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merna6 mouhamed |
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I write my email but not opened
August 26, 2003
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