Originally Posted by Whatsreal
I use no formula, but an old trick. All you need is to know the size of your sensor in milimeters andto have aruler. Take a picture of the milimeter side of the ruler located at minimal working distance from the lens. If you re using eg a full frame sensor (36mm widex24mm high) and photograph, say, exactly36mm of the ruler across of your picture you get exactly 1:1.The less of the ruleryou can squeeze on the frame the more magnification your lens/ lens+tube will give you.Simpledivision of thewidth of the sensor by the length of the ruler in the frame will tell you the exact magnification. I like this method becauseone does not have to worry aboutvariations ofdifferent lenses.
Rulers rule![Y]
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