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Old 11-04-2010, 07:33 PM
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Robert9 (Robert)
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Join Date: Dec 2008
Location: Mt. Waverley, VIC, Australia
Posts: 741
Hi Peter,
In the good old days of 35mm film photography, a "standard" 1:1 magnification was accepted as being a photo shot with a 50mm lens. A 200mm lens therefore gave a 200/50 = 4x magnification. In these terms, if you take the standard lens on your DSLR as giving a 1:1 image mag. then by dividing the focal length of your scope by the focal length of your "standard" lens, you should get a reasonable idea of the mags.
I have also heard that a truer standard lens focal length is that numerically equal to the diagonal of the image frame. In the case of a 35mm frame (24 x 36mm) this would be 43mm. Hence a 200mm lens would have, by this method, a mag of 4.3x
Hope that helps a bit.
Robert
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