Phase-de­tec­tion AF

Digital Camera World - - CAMERA COLLEGE -

The light re­flected down to the AF mod­ule is sep­a­rated by a mi­crolens, which pro­duces a pair of off­set images on the AF sen­sor. The dis­tance or ‘phase dif­fer­ence’ be­tween the two images is mea­sured, and the cam­era de­ter­mines whether the lens needs to be fo­cused fur­ther away 1 or closer 2 and by how much 3, in or­der to make the two images line up 4. As a re­sult, phase-de­tec­tion puts in a fast per­for­mance, although like con­trast­de­tec­tion AF it can strug­gle in low light.

AF sen­sor

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