Close-up math

Started May 3, 2014 | Questions thread
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Close-up math
May 3, 2014

The Olympus 12-50 specs include a maximum magnification of 0.72x. Given that a m43 sensor is 17.3mm x 13mm, I would have thought the minimum field width would be 24mm (17.3/0.72). However, the smallest I can get in focus is about 33mm across (macro mode, manual focus with ring spun clockwise).

What am I doing wrong?

I'm asking because I'm trying to figure out the diopter strength or extension tube length to get a minimum field width of about 35mm with the Olympus 40-150. With a max magnification of 0.16x and a MFD of 900mm, I would have thought I'd need 4-5 diopters or 60mm of extension. Of those two, I'd choose 4-5 diopters (60mm of extension would lose too much light). That's assuming my math and understanding are correct.

Close-up calculator at

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