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: Just had my D800 serviced for the defective left AF bank
In reply to Michael Benveniste, Oct 14, 2012

Michael Benveniste wrote:

Think about this for a second.  While such a camera correction could change the overall front- or back-focus characteristics of the combined system, it would do so at every focal length and with every lens, not just some.>

Yes, which is why all lenses need to be re-tested and re-calibrated.  And depending on each lenses unique characteristics, the combinations will vary from lens to lens.  Think about that ... could you be stating the obvious?

>So either the problem was there all along and you never noticed, something happened to the lens in the interim, or the result due to experimental error.   Before spending your money, I suggest trying to eliminate the last factor.>

I suspect the first, that the characteristic has been there all along, and is more revealing with the resolution of a D800 vs. D700.  For example, I was never completely confident in my 24-70 wide open on my D700, and attributed that to the lens just being a little soft in those situations. Using it on a D800 made this more evident, and pushed me to more in depth testing.  That revealed a significant variation in the AF  unit ... which Nikon agreed was defective and repaired under warranty.

I never extensively tested by 70-200 on my D700, and even the D800, until now.  I use this lens mostly between 150 and 200mm, and in the times I have used this lens between D800 repairs, I've been entirely between 175 and 200mm.

My 24-70 went from +12, to between 0 to +2 post-D800 repair. I trust the lens because of the recent service.  It is better than new.

I suspect the same is basically true with the 70-200:  it needed +20 @ 200mm pre-D800 repair, and now needs 0. I re-tested again, found a few tweaks to change in the process.  What I'm finding now consistently is +16 @ 70, to 0 at 200. So post D800 repair, going from +20 to 0 at 200mm follows the repair on the body.

>None of the Nikon lens manuals I own recommend or even mention periodic servicing.

It's somewhat common for professional sports photographers, because of the level of abuse their lenses are expected to endure.  Elements get decentered or nicked or physical items such as lens mounts and switch gear get jarred and bent.  I've never heard of a front- or back-focus change without any other symptoms, but I suppose it's barely possible.

Absent such trauma though, most lenses should only need cleaning.  In the 30-odd years I've owned SLR lenses, I've sent lenses in to have chip replacements, motor replacements, tighten the zoom action, and repair the aperture action.  The only optically related repair I've had done was after a fall.  The only lenses I know of which require preventive maintenance are those with built-in leaf shutters, such as those made for (some) medium format cameras.  Even there, my Pentax 135mm f/4 LS has yet to need such service.>

Perhaps you are lucky, or you have benefited by the legendary Nikon QC.  Having used Canon lenses for over 20 years, sending in lenses for service at regular intervals is not uncommon ... even for non-sports shooters.  Things have a way of working and loosening up.  I agree that purely optical problems need a cause to develop, but other factors from normal wear can reveal an optical problem over time.

>While it's not uncommon for different "ends" to yield different fine-tune results, it would be extremely unusual to see the magnitude of difference you measured. Nor would any repairs done to the camera account for it.>

Unless the lens has a defect. And no one has suggested the camera has anything to do with that.

I suggest having someone else do the retest for two reasons.  The first is that if your testing technique has a "hole" in it, you will get the same wrong result repeatedly.  The second is observer bias.  No offense, but scientists use double blind studies for good reason.  I think there's a real chance that your beliefs on how common it is to need lens adjustments may have induced such as bias.>

I'm pretty comfortable with something like this, which is not that complicated.  Maybe you like to have others check these kinds of things for you, and that's fine ... your comfort level kind of thing.

I don't have a financial interest in how you spend your money, so if you want to spend it on a likely placebo that's between you and your wallet.  We all have a financial interest in minimizing unnecessary warranty service, though, since the cost of that service inevitably ends up being reflected in the price of gear.>

Thank you for allowing me to spend my money how I choose ... dad? What a condescending and boorish comment.  And attitude.

>Do all of us a favor and have someone else verify your results.>

Who's "us"?

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Nikon D750 Tamron SP 70-300mm F/4-5.6 Di VC USD Nikon AF-S Nikkor 85mm f/1.4G Nikon AF-S Nikkor 24-120mm f/4G ED VR Nikon AF-S Nikkor 50mm f/1.8G +1 more
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