16-50 Nex 6 focusing issue with PDAF

Started Jan 4, 2013 | Discussions thread
missingendpoint
Regular MemberPosts: 126
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Re: 16-50 Nex 6 focusing issue with PDAF
In reply to Bart Hickman, Jan 6, 2013

Bart Hickman wrote:

missingendpoint wrote:

I do not have a phase detect nex [just two 5Ns which serve me fine today] -- but given that phase detect is essentially an open-loop system [the lens is driven 'directly' to the point where the controller expects focus] and not close-loop like contrast focus [the lens 'hunts' as the controller maximizes contrast], I'm surprised the nex pdaf [apparently?] does not include per-lens focus fine-tuning like many dslrs. Could this be a hidden service option? While I'm not sure fine tuning would help if the problem is not linear across all focal lengths, I haven't seen anyone mention the basic capability.

This is not true. PDAF also "hunts" for maximum contrast (or, more specifically, image alignment) on the AF sensor. The main difference is the mis-alignment on the AF sensor gives you much more accurate information about both direction and amount of mis-focus with just a single measurement whereas CDAF only gives approximate information about the amount of mis-focus and no information on the direction. So they are both servo-systems, but the PDAF converges much more quickly.

And since the AF sensor is on the image sensor on the NEX-6, there are very few ways for the two to disagree (mostly involving defective lens optics which clearly isn't the case with the O.P.'s 16-50). The whole thing is a bit baffling frankly.

Bart

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I'm sorry to hear the nex phase detect still hunts when there is sufficient light for it to function.

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