Using AF Tuning on a 70-200: when to send in for repair?

Started Oct 13, 2012 | Discussions thread
ne beginner
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Re: Using AF Tuning on a 70-200: when to send in for repair?
In reply to Leonard Shepherd, Oct 15, 2012

Leonard, as stated in response to your earlier comment, distance between lensalign target and camera were changed for each focal length tested, using the ranges recommended by lensalign.  The tool was aligned properly as well.  I did re-do the test based on lighting however, and results were consistent but slightly different numbers.

I have posted test images in a response to Mike above.  I have also stated that I believe this condition likely has been there all along, for two reasons. First, I rarely shoot this lens below 100 ... the vast majority images I have are well above 100mm ... most are closer to 200mm.  Second, I found a test image using lensalign, taken pre-D800 repair, using +20 @ 70mm, showing the front focus was still evident.   Guess I never looked closely or paid attention ... most of my attention was at 200, where I shoot most with this lens.

So +20 was not enough at 70mm back then, but it did correct it at 200.  I have posted a sample image taken at 190mm and +20, which is sharp at the AF point (center bank). I have also posted post-repair lensalign tests showing zero AF at 70 and 200mm.  Clearly this lens needed +20 pre-repair @ 200, and now needs 0. Not so at 70mm.

You may question lensalign as a target, but for center AF points I don't believe there is an issue. I know many people have similar views.

My conclusion is that this lens has an issue that probably existed all along, unless it got a good bump somewhere that I don't recall or was unaware of.

It also does not sound like this lens should vary that much from one end to the other.  I know that is a condition common to zooms, and was hoping for more commentary on that. I posted this question on another forum, and the responses were more in that direction.  I know many recommend tuning zooms at either the middle FL, or at the end you use most, but the swing here is too great to make that viable.  I often shoot at 2.8.

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