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04. What is the basic formula for the conditions under which an image is in focus?




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This article is from the Photographic Lenses FAQ, by David Jacobson with numerous contributions by others.

04. What is the basic formula for the conditions under which an image is in focus?

There are several forms.

        1/Si + 1/So = 1/f      (Gaussian form)
        (Si-f)*(So-f) = f^2    (Newtonian form)

 

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