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I think the equivalent focal length of the eye is about 50mm, and is
it true that a 5 mm eyepiece therefore is a loupe or magnifier of 10 (50
divided by 5) power? That's what I remember fom my kindergarden optics class
taken in the paleolithic age.
glenn shaw
But that's not what matters. What matters is the
size of the image on the retina. Normal viewing distance is normally taken
to be 250 mm, so 250/F is the "power" of a magnifier. Focal length 5 mm =
50 power.
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