Quote:
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magnification = ext tubes / focal length + 1 x 1.6 (crop factor) = 2.8444444
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I'm not sure about the +1 part (I remember the guide that when extension + focal length you get 1:1)
In addition I think it applies to having the lens focused at infinity. If the lens is focus closer the ext tubes part becomes Total extension as focusing the lens adds extension internally.
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Mike
Pentax K5ii & Panasonic G5 user (with far too many bits to list)
Member of North Essex Photographic Workshop
Also online with PentaxUser.co.uk, Flickr, MU-43, MFLenses...
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