I know that aperture and DOF are inversely proportional. But, can anybody explain to me the Physics/Optics behind that? What's the mathematical relation that relates aperture with DOF?

  • It's primarily a geometric relation that explains it. Of course that geometric relationship can be expressed in mathematical terms, but it is first and foremost a geometrical relationship. – Michael C Aug 21 '15 at 1:37

Wikipedia has all of the DoF formulae you probably ever need. You may now begin to see why optics is a field of physics unto itself.

You aren't going to be able to learn these equations and do them in your head to map an ƒ number to a depth of field in, say, feet. This is why there are so many DoF calculators floating around. I wrote one of many.

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