why micro focus adjustment ?

Started Feb 25, 2013 | Questions thread
FinDERP Forum Member • Posts: 56
Re: why micro focus adjustment ?

From my (very limited) understanding of phase detection autofocus I believe this might be because the AF sensor takes a measurement of the 'out of focusness' of the given AF point, then decides how far the lens needs to move and moves it. It doesn't necessarily check the accuracy of the mechanical motion after it has happened because it has calculated the amount of focus throw needed before actually moving the lens itself - you can no doubt see that if the motor or gearing in the lens system isn't totally accurate or if there is no checking after the lens has moved or even the checking of the focus or distance moved by the lens is off slightly then you will produce either inconsistent or perhaps consistently out of focus images. A small instruction telling the camera to move the lens X units further/less every time it focuses could correct that mechanical maladjustment!

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