Nikon D7100 left focus issue

Started Apr 19, 2013 | Discussions thread
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Mako2011 MOD
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Best they can
In reply to PepsiCan, Apr 23, 2013

PepsiCan wrote:

Mako2011 wrote:

PepsiCan wrote:

lock wrote:

I can see a back focus on the left side picture with the 70-200, and what he should have done is take a series of 10 on both the left and right side to confirm the difference. That would rule out random error of the AF sensors. That is the only real thing he should have done to make his judgement more solid. Other than that, his pictures show more information pointing at a left af sensors issue than the opposite.


And compare those shots against CDAF focussed shots taken in Live view. That would unambiguously rule out any lens issues.

You can still have lens issues that affect PDAF but are overcome by CDAF

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My opinions are my own and not those of DPR or its administration. They carry no 'special' value (except to me and Lacie of course)

Yes, but that is not why I say to test with CDAF. CDAF is a better reference against which to compare everything else than when you compare PDAF shots with each other. Once you have a reference, you can safely draw conclusions.

Sure, but CDAF comparisons to PDAF do not "unambiguously rule out any lens issues".

When you compare two pictures both taken with PDAF, you cannot exclude the lens perse as the cause of a focus issue, so you do not know for sure whether the lens or the camera's focus system is the issue (although you will have a degree of likelyhood).


With a CDAF reference any statements made will carry more weight because you're eliminating possibilities. And note that the CDAF test should be added to what Lock already described. It cannot proof much in itself.

Sure...but  CDAF compared to PDAF only shows if there is a difference in the results regards focus of the two systems. It does not positively rule out a lens, body, both, or even a light issue. Just as the red box in viewNX2 doesn't really show what the focus array locked onto.

My point is not that you cannot assert focus issues with PDAF-only tests. My point is that when you stake a claim on an internet forum, you need to be a bit more diligent in what you do.

That would be nice. We always hope folks do the best they can

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My opinions are my own and not those of DPR or its administration. They carry no 'special' value (except to me and Lacie of course)

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