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Proper focus??
Hi Gurus,
I need a help to compute the focus of a lens. I want to make sure my camera can see a 10 feet by 10 feet table from about 9 to 12 feet away. So what is the proper focus of the lens that I should choose? Current, I have a 8.5mm focus lens, it can see 42in height and 31in width from 72in away. So I just assume everything is linear, then: if I want to see from 9 feet, the proper focus is L. We have 8.5/L=D/9, where D/6=10/(31/12) Then L=3.3 mm Is it correct? Please help me to check. Thanks. Regards, Zhen |
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