why micro focus adjustment ?

Started Feb 25, 2013 | Questions thread
Allan Olesen
Senior MemberPosts: 2,256
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Re: why micro focus adjustment ?
In reply to theswede, Feb 25, 2013

theswede wrote:

All of this is complicated by focus plane offsets shifting when a lense is zoomed (or even stopped down, though that is seldom an issue to to DOF increase)

Actually, when you use a lens fully open, it is stopped up compared to what the AF sensors saw. And when it is stopped up, DOF decreases. So I think that this is a very common phenomena, and as far as I know, all AF lenses have built-in correction tables which tell the camera how much to correct for the aperture dependent focus shift.

Remember that most cameras have PDAF sensors which see light from light paths around f/5.6-f/6.3.

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