Nikon D7100 left focus issue

Started Apr 19, 2013 | Discussions thread
Mako2011
Mako2011 MOD
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In reply to fireplace33, Apr 23, 2013

fireplace33 wrote:

Hi Mako,

That sounds quite logical and would point to a problem with the lens!

In fact the same problem with 3 different lenses but that is however, to say the least, quite a coincidence?

Remember, I'm simply explaining why issues with PDAF can be a body, lens, or both issue...and comparing to CDAF doesn't often tell you which area the problem is in.

On the other hand, applying the logic and conclusion from Pepsican  in this thread, to my results, it would tell me exactly the opposite??

..."That the camera's PDAF system is miscalibrated"

So I'm still confused..  (camera or lens?)

Don't be, If you test properly and the problem is consistent with all lens, your body most likely needs a bit of help. If the problem isn't consistent across all lenses, then it may be a combination of problems.

Pepsican said that after doing the tests, as I did them,...

There are now couple of possible outcomes.

PDAF = CDAF = in focus --> There is no issue

True, but fine tune may still be needed to but the lens in the center of the DOF for PDAF.

PDAF Center = CDAF center but either Right PDAF <> Right CDAF or Left PDAF <> Left CDAF. We have a problem with the PDAF system.

Or the lens or both. That assumes proper testing in good light using good procedures. (simulating how Nikon does it)

Your center is sharp, in live view things are also sharp but the PDAF system cannot get sharp focus on the outer edges.

Depends, if left and right sides are soft with a wide angle fast lens using PDAF, that is not uncommon and may be normal. Depends.

This is the symptom that D800 users had and it is known as the left-focus issue. Basically, your PDAF system is miscalibrated and you need to send the camera in for a tune up.

Yes

The third possibility happens when both PDAF and CDAF do not give you sharp results. That points towards a problem with the lens rather than the camera. There may be some decentering if one side is weaker than the other. Or if left, right and center all show out-of-focus results, there may be front- or back focus. Which one it is, requires further testing.

That is most likely a lens problem if it only occurs with one lens. There can still be a camera issue though... if it occurs with all lenses. Slow glass can mask a problem with focus.

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