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Third repair attempt fails

johno

St. Louis, US
525 posts

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johno Silver Member Nikonian since 23rd May 2006
Tue 25-Dec-12 03:58 PM

I got my D800 back from its third repair attempt. It is still in severe front focus. +20 fine tune makes it much better but not quite crisp.

Repair one for left focus: no change

Repair two for left focus: left focus appears better; camera front focuses across all sensors

Repair three: no change

I was told it was going to be replaced, but it wasn't.

There must be an imposter from Canon working in Nikon's tech service department. That's the only thing that makes sense.

Is there any hope of getting this resolved?

Thanks

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TomCurious

Bay Area, US
2352 posts

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#1. "RE: Third repair attempt fails" | In response to Reply # 0

TomCurious Registered since 03rd Jan 2007
Tue 25-Dec-12 05:02 PM

I have read in several places that Nikon would replace a camera or lens after 3 failed repair attempts, but you won't find any official statement from Nikon to that effect, and there is surely always some discretion.

But in any case, I would first make sure the camera really has an issue. I.e. does it front focus with several lenses, and these lenses focus find on another body? That would be the easiest way to establish that. If you're sure it's the camera, I would send it in again, point to the 3 failed attempts and demand a replacement.

Tom
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johno

St. Louis, US
525 posts

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#2. "RE: Third repair attempt fails" | In response to Reply # 1

johno Silver Member Nikonian since 23rd May 2006
Tue 25-Dec-12 07:45 PM

Thanks

It happens with every lens. Al Nikon lenses, all but the 28-300 being "professional" Nikon lenses.

I do not have another body to compare them to, but they all worked fine with the center and right autofocus sensors on this camera, until after repair number 2.

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TomCurious

Bay Area, US
2352 posts

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#3. "RE: Third repair attempt fails" | In response to Reply # 2

TomCurious Registered since 03rd Jan 2007
Tue 25-Dec-12 08:20 PM

Sounds very much that they didn't repair it right, then, and perhaps the camera has some more serious issue. If they had repaired it right the first time, then when they got the camera for the 2nd and for sure the 3rd time, they should have just checked it and concluded there is nothing wrong with it. I have seen such reports as well, and if that were the case, I would have advised you to check the focus and your lenses more carefully. But if they actually did perform a repair the 2nd and 3rd time around, it would mean there really was an issue with their own previous repair attempts.

Anyway, I hope you get it resolved and a replacement. I would not accept a 4th attempt in this case.

Tom
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venusian

US
186 posts

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#4. "RE: Third repair attempt fails" | In response to Reply # 3

venusian Registered since 17th Dec 2008
Tue 25-Dec-12 09:59 PM | edited Tue 25-Dec-12 10:01 PM by venusian

I would take this issue to Corporate Consumer Affairs and speak to a manager. Explain what has happened and ask for a brand new replacement camera with zero acutations.

I feel that anything short of that approach will be very frustrating for you. You paid for a new camera and expected it to work. They are obliged to live up to their side of the bargain...especially after 3 failed attempts at repairing it.

Before speaking to a manager briefly outline the camera's problem(s) and the repair failure history and tell Consumer Affairs that you want to have a written account of the problem on record and to make sure your phone call doesn't get lost in the corporate maize.

By emailing or faxing your problem/repair history to a manager, you also have a record of your contact/call.



Nick (Roxbury, Connecticut Nikonian)

airlaw

Seattle, US
61 posts

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#5. "RE: Third repair attempt fails" | In response to Reply # 4

airlaw Gold Member Nikonian since 23rd Sep 2002
Fri 18-Jan-13 06:33 AM

that's a great idea. Cc the CEO as well.

Kit

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BR

Glen Mills, US
542 posts

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#6. "RE: Third repair attempt fails" | In response to Reply # 0

BR Registered since 17th Nov 2006
Fri 18-Jan-13 11:50 PM

Sorry to hear about this but, based on my interactions with Nikon service, it is not surprising. I would take the advice to try to escalate it to someone higher up, if possible. You know what they say about doing the same thing over and over and expecting different results.

It seems that at some point Nikon bean counters decided to de-emphasize service and live with the potential negative publicity.

Barry

airlaw

Seattle, US
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#7. "RE: Third repair attempt fails" | In response to Reply # 0

airlaw Gold Member Nikonian since 23rd Sep 2002
Mon 21-Jan-13 06:26 AM

Johno what are the first 5 digits of the serial number on the camera so we can see if the camera is from new production or not.

Thanks.

Kit

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johno

St. Louis, US
525 posts

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#8. "RE: Third repair attempt fails" | In response to Reply # 7

johno Silver Member Nikonian since 23rd May 2006
Mon 21-Jan-13 11:57 AM

I am not with my camera for a few days. The camera was purchased the first day they came out.

I'm beat down over this. Nikon will not communicate about it, and I feel completely powerless to do anything about it any more.

My thoughts are turning to selling all of my Nikon gear and switching to Canon. But that has obvious drawbacks.

What I think happened is that when I sent back the camera I forgot to set it back to zero on the auto focus fine tune. So the Nikon tech "tested it" at +20, and sent it back off by that much more or less.

Their phone people are little more than script readers, unable to communicate at more than a basic level, and with strict orders to not involve any colleagues who are in a position to communicate complex thoughts or make any decisions.

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duh59

Rochester, US
591 posts

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#9. "RE: Third repair attempt fails" | In response to Reply # 0

duh59 Silver Member Charter Member
Tue 22-Jan-13 09:52 PM

Hi John, I am very sorry that you are going through this . I hope that Nikon makes it right for you, and soon! Good luck

Virge

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Gromit44

UK
730 posts

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#10. "RE: Third repair attempt fails" | In response to Reply # 8

Gromit44 Registered since 04th Jan 2012
Wed 23-Jan-13 12:23 PM | edited Wed 23-Jan-13 02:51 PM by Gromit44

>What I think happened is that when I sent back the camera I
>forgot to set it back to zero on the auto focus fine tune. So
>the Nikon tech "tested it" at +20, and sent it back
>off by that much more or less.

That's hardly your fault - the Nikon Tech should have reset it to zero before doing anything.

johno

St. Louis, US
525 posts

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#11. "RE: Third repair attempt fails" | In response to Reply # 9

johno Silver Member Nikonian since 23rd May 2006
Wed 23-Jan-13 01:27 PM

Thanks for the kind words. My warranty runs out in a couple of months. Maybe they are trying to run out the clock.....

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wesmannmsu

US
302 posts

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#12. "RE: Third repair attempt fails" | In response to Reply # 11

wesmannmsu Silver Member Nikonian since 19th Mar 2011
Wed 23-Jan-13 01:59 PM

each Repair some with its own limited warranty, return it again right way.

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agitater

Toronto, CA
4551 posts

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#13. "RE: Third repair attempt fails" | In response to Reply # 0

agitater Gold Member Donor Ribbon awarded for his very generous support to the Fundraising Campaign 2014 Nikonian since 18th Jan 2007
Wed 23-Jan-13 02:10 PM

I'd advise the following.

1. Do a full reset. Put the camera back to all factory defaults. Then double check all the menu entries (especially AF fine tune) to ensure everything is zero'd out.

2. Call Nikon and tell them that you're having a service completion problem. Ask to speak with the head of service to explain the matter and then tell him or her that you want the camera operating within spec. A request to the head of service to follow the trouble ticket and service procedure to ensure proper completion is also advisable.

3. Get your authorization and send in the camera. Include in the insured shipping package a letter that re-states your conversation with the head of service. As a general rule, I personally wouldn't bother complaining or pointing out any perceived failures on Nikon's part. As right as I might be in the same situation, dressing them down wouldn't help my case.

4. With the direct name and address of the head of service, write a letter re-detailing the problems, add a request to replace the camera if it cannot be brought reliably into spec, and then transmit the letter by registered mail or by courier.

Good luck.

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johno

St. Louis, US
525 posts

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#14. "RE: Third repair attempt fails" | In response to Reply # 13

johno Silver Member Nikonian since 23rd May 2006
Wed 23-Jan-13 03:27 PM

Thanks

I will follow your suggestion to the letter.

Much appreciated.

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ZoneV

US
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#15. "RE: Third repair attempt fails" | In response to Reply # 14

ZoneV Silver Member Nikonian since 07th Jan 2005
Wed 23-Jan-13 03:53 PM

According to Thom Hogan today, Nikon has some quality control issues these days, especially with AF.

Nikon user since 2000

agitater

Toronto, CA
4551 posts

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#16. "RE: Third repair attempt fails" | In response to Reply # 14

agitater Gold Member Donor Ribbon awarded for his very generous support to the Fundraising Campaign 2014 Nikonian since 18th Jan 2007
Wed 23-Jan-13 05:28 PM

>I will follow your suggestion to the letter.
>
>Much appreciated.

You're welcome. I'm very interested to hear the, hopefully, final outcome. It should be either a perfectly serviced camera very shortly or a tested replacement very shortly.

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rplst8

Johnstown, US
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#17. "RE: Third repair attempt fails" | In response to Reply # 15

rplst8 Silver Member Nikonian since 18th Dec 2008
Wed 23-Jan-13 05:30 PM

Yes, I hope folks read Thom's post and check out the Reikan FoCal website with the data he speaks of.

http://www.reikan.co.uk/focalweb/index.php/online-tools/lenscamera-information/

The data is very telling.

--
RL

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mgd7

New York, US
104 posts

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#18. "RE: Third repair attempt fails" | In response to Reply # 13

mgd7 Registered since 06th Mar 2012
Thu 24-Jan-13 08:26 PM

Looks like I am in a similar boat as the OP, as Nikon has my D800 for the 3rd time right now only they claim they can't find anything wrong with it. Unfortunately, it seems that they are unable or unwilling to read my letter explaining what the fault is. (In my case, after the first--successful!--AF repair, I could no longer MF based on how sharp the image is on the focusing screen. (I did careful testing after consistently missing MF.) Second repair botched the AF again without helping MF.)

When I get the camera back in hand, I will try your procedure as well. Thanks for the suggestion.

I have a D800E that can AF and MF, so I know how good life can be....

BR

Glen Mills, US
542 posts

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#19. "RE: Third repair attempt fails" | In response to Reply # 18

BR Registered since 17th Nov 2006
Thu 24-Jan-13 09:17 PM

Unfortunately your experience sounds all too familiar. I sent in my D200 a couple of years ago with a detailed explanation. When I heard back from them, it was in the form of a terse statement about a shutter problem, along with mysterious acronyms. The problem I was having had nothing to do with the shutter, as they eventually agreed, so they also apparently didn't bother to read what I submitted.

Barry

johno

St. Louis, US
525 posts

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#20. "RE: Third repair attempt fails" | In response to Reply # 19

johno Silver Member Nikonian since 23rd May 2006
Wed 30-Jan-13 04:23 AM

I have reached out to Nikon to find the name of the service manager. Still waiting.

Meanwhile I reset the camera as suggested, deleted autofocus fine tune settings, and I shot some fresh focus fine tune-style images, without subsequent adjustment.

I found my 24-70 focuses a full 10 inches short at about 6 feet from the slanted-ruler target. My old 50 mm 1.4 also is 8 or 10 inches short. Strangely, my 105 2.8 and 85 1.4 are within 2 inches or so. I didn't bother with the 14-24.

As before, the fine tune is out of possible adjustment range.

Is self-immolation or a hunger strike a possible way to get resolution from Nikon? One of the batteries originally shipped with the camera could serve as an ironic ignition source.

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briantilley

Paignton, UK
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#21. "RE: Third repair attempt fails" | In response to Reply # 20

briantilley Gold Member Deep knowledge of bodies and lens; high level photography skills Donor Ribbon awarded for his support to the Fundraising Campaign 2014 Nikonian since 26th Jan 2003
Wed 30-Jan-13 08:05 AM

>I found my 24-70 focuses a full 10 inches short at about 6
>feet from the slanted-ruler target.

This may have come up before, but did you try with a flat target parallel to the camera sensor? Angled AF targets with detail at different distances from the camera are a big cause of inconsistency in focus testing.

Brian
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bkinthebay

bkinthebay, BE
409 posts

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#22. "RE: Third repair attempt fails" | In response to Reply # 21

bkinthebay Registered since 27th Feb 2010
Wed 30-Jan-13 10:27 AM

Hi Brian,

This is exactly the motivation behind the alternate testing method I have documented here:

https://www.nikonians.org/forums/dcboard.php?az=show_topic&forum=430&topic_id=19368&mesg_id=19368&page=9

Cheers,
Bernard.

agitater

Toronto, CA
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#23. "RE: Third repair attempt fails" | In response to Reply # 22

agitater Gold Member Donor Ribbon awarded for his very generous support to the Fundraising Campaign 2014 Nikonian since 18th Jan 2007
Wed 30-Jan-13 12:53 PM

I think Bernard's efforts are quite interesting. The problem is that I can use his target method to fool a Canon 5D, Canon T3i, Canon G1 X, Fujifilm X-Pro 1, Nikon D700, D5200, D7000 and a D800 into consistently front- or back-focusing. It leaves the impression that the AF in each body needs fine tuning. But when I check the same cameras using the same lenses shooting a known-flat chart that is mounted parallel to the plane of each camera sensor, AF becomes consistently accurate. How much physical bias by the photographer at home doing such testing figures into this sort of DIY effort is another unkonwn factor, but a variable still. With a less-than-optimal parallel/plane test target I can also force AF inaccuracy.

There's no doubt that Bernard's chart method can be accurately used, but it takes so much effort, careful lighting and attention to focus point positioning (in order to get a truly accurate focus lock in the first place) only to almost always confirm the degree AF accuracy that is so much easier and faster to confirm using a parallel/plane testing method.

By the way, sufficient static charge buildup or discharge on a table surface can gradually lift an unsecured paper target sheet or gradually lower it - a few mm in each case - to render all of the AF testing effort worthless.

For a camera that fails the parallel/plane chart focus testing method, AF fine tuning might be needed, in my opinion. The main problem with any sort of AF fine tuning is that the camera owner has to assume that the camera's AF system will always react precisely the same way at each and every press of the AF-On button or shutter button. As many tests published by LensRentals and other testers have shown - particularly in the most extensive sample testing of all the top camera bodies over the past couple of years - AF systems are fundamentally inconsistent in terms of absolute accuracy. Sequences of identical test shots with the same camera and lens results in a range of results which reflect the engineering/design tolerance variables inherent in the AF system. The point is that if we then apply AF fine tuning adjustment to that camera and lens combination, we're not reducing the variability inherent in the design of the AF system, rather merely shifting some median point to another location. But the variability inherent in the AF system remains.

It makes more sense, IMO, to adjust our shooting habits to the particular combination of engineering/design/assembly variation of the particular camera and lens we're using, and to adjust our focus technique over time as we come to understand how the camera and lens react in different shooting situations for different kinds of subjects. That takes time. As we get to know the combo's specific variables, we inevitably refine and improve our use of the particular camera and lens. Only a grossly misadjusted camera and/or lens will stymie such efforts and such gross misadjustments are very rare.

After having gone through somewhere north of 60 Nikon digital SLR bodies (personal use and review use) and around 30 Canon DLSR bodies (personal use and review use), I have only encountered five with a bad AF system (two Nikon, three Canon). The first Nikon one was my original D700 - the AF system simply failed during the first week I had the thing. My dealer exchanged it over the counter for a perfect one which I used for years. The second Nikon AF system problem occured with a D7000. In the second D7000 I had, the AF system seemed to be completely uncalibrated - an obvious error that escaped the factory. The same dealer exchanged it over the counter for a D7000 which turned out to be perfect. I've still got it. Great camera.

The three Canon bodies were a 30D, 60D and a 1D MK III. The 30D was mis-calibrated at the factory. The 60D had a misaligned mirror. The 1D MK III simply wouldn't lock focus accurately without sufficient prayer, sprinkling of magical pixie dust, and repeatedly murmured incantations. The 30D and 60D were review units and were each exchanged by the PR rep for good ones. The 1D MK III was exchanged by my dealer for a unit that had been unpgraded by Canon (a sub-mirror assembly replacement IIRC). Worked perfectly.

I think that, except in exceedingly rare situations in which a camera escapes the factory having been calibrated at or near one extreme of its AF adjustment tolerances and with the owner then using a lens that is at or near a complimentary extreme of its calibration tolerances as well, focus accuracy is more of a photographer adjustment than a technical camera AF system adjustment. I admit that the biggest difference between my results may be based on the fact that I'm a street shooter - tripods just aren't in my photographic vocabulary - and natural adjustment based on familiarity with the camera's variability in different shooting situations may be even more important than it is to photographers who work with a tripod more often than not. A good, sturdy, well adjusted tripod & head at least reduce the impact of some of the variables in any shooting situation. Then again, AF testing at home is always done on a tripod.

I realize that there are photographers who are tweaking every aspect of their camera performance, and I fully respect the effort. I think anybody who spends the time to squeeze every drop of performance out of their photography gear deserves respect. Nonetheless, I think it's unrealistic to expect camera AF systems (read: all AF systems in use today across all makes and models) that struggle with texture detail at 45 degree angles (or other severe angles) in real shooting situations in almost all lighting to produce test results reliably consistent enough to form the basis of AF fine tune adjustments during DIY home testing.

I believe it's possible that Bernard's approach absolutely nailed an AF problem he was experiencing. Every such test method works for somebody, somewhere. But I also believe that duplicating his method to achieve some perceptible improvement in AF accuracy is too inherently problematic to be worthwhile. These cameras are amazing, but their most conceptually and physically difficult aspects to refine are the AF systems - ironically the one thing in particular that we rely on to help produce the photos we like best. AF systems are not simply mechanical affairs, rather combining mechanical systems with optical systems, management software and digital processing. Expecting absolute consistency out of them is unrealistic and, at least at the current state-of-the-art, impossible.

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bkinthebay

bkinthebay, BE
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#24. "RE: Third repair attempt fails" | In response to Reply # 23

bkinthebay Registered since 27th Feb 2010
Wed 30-Jan-13 01:16 PM

>I think Bernard's efforts are quite interesting. The problem
>is that I can use his target method to fool a Canon 5D, Canon
>T3i, Canon G1 X, Fujifilm X-Pro 1, Nikon D700, D5200, D7000
>and a D800 into consistently front- or back-focusing. It
>leaves the impression that the AF in each body needs fine
>tuning. But when I check the same cameras using the same
>lenses shooting a known-flat chart that is mounted parallel to
>the plane of each camera sensor, AF becomes consistently
>accurate. How much physical bias by the photographer at home
>doing such testing figures into this sort of DIY effort is
>another unkonwn factor, but a variable still. With a
>less-than-optimal parallel/plane test target I can also force
>AF inaccuracy.
>
>
Hi Howard,

Could you explain how do you manage these bodies, properly adjusted, to poorly focus on the test chart using the procedure I described? That way, I can maybe workout a better one . It would be great if you could post an example,maybe in the original thread not to pollute the current one...

Regards,
Bernard.

Vox Sciurorum

Newton, US
240 posts

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#25. "RE: Third repair attempt fails" | In response to Reply # 18

Vox Sciurorum Registered since 18th Oct 2007
Wed 30-Jan-13 01:20 PM

>Unfortunately, it seems that they are unable or unwilling to read my
>letter explaining what the fault is.

I had the same experience. My explanation of a problem with flash commander mode was condensed to "flash doesn't work" in the service order. Nikon replaced my camera the fourth time I sent it for repair.

agitater

Toronto, CA
4551 posts

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#26. "RE: Third repair attempt fails" | In response to Reply # 24

agitater Gold Member Donor Ribbon awarded for his very generous support to the Fundraising Campaign 2014 Nikonian since 18th Jan 2007
Wed 30-Jan-13 06:15 PM

>Could you explain how do you manage these bodies, properly
>adjusted, to poorly focus on the test chart using the
>procedure I described? That way, I can maybe workout a better
>one . It would be great if you could post an example,maybe
>in the original thread not to pollute the current one...

It's easy to cause a mis-focus. A large percentage of the time, the focus point that a tester has positioned on a 45 degree target sheet is not actually locking on at that chosen focus point. The camera may signal a confirmation (with the focus dot), but the resulting shot appears mis-/front-/back-focused because the lock signal was an approximation. This has been demonstrated many, many times in other threads on Nikonians - most or all of which predate your other thread on the subject. Nothing new here. Once I've done somewhere between 40-50 shots with a single setup, the variability begins to show up in the results charting. Once I've done upwards of 100 test shots with a single setup, the AF system variability is incontrovertible. If someone wants to go to those lengths to find an AF fine tune setting that can improve overall performance, go for it. But test shot sessions of 10, 20 or even 30 shots with a single setup usually don't tell the photographer anything useful. In the middle of testing on a very hot or very cold day, open a window to either heat up or cool down the room and watch the variability range shift every so slightly.

Considering that a moderately well used Nikon DSLR in the hands of an active amateur photographer might be used to shoot a thousand photos a month, AF fine tune targeting results based on a minimum of 100 shots with a specific set up is a basic drop in the bucket. But it's enough to get a real sense of how well or how poorly a particular AF system is performing. Most people who do such extensive AF test target shooting using parallel/plane setups, usually then back away from any AF fine tune adjustment because they're suddenly more cognizant of the inherent variability of the AF system in the first place.

I hesitate to contribute samples to the discussion of a calibration methodology with which I fundamentally disagree. The reliance on focus point positional confirmation in software such as Capture NX/NX2 is also problematic. I'm not suggesting for one minute that our cameras and the post-processing software we use is totally problem ridden - far from it actually. I'm just suggesting that I haven't found a testably duplicable AF system problem in something like 85 different camera bodies (or more, if I also take into account Sony, Olympus and Panasonic bodies). I've just found the occasional broken camera plus a couple of DOA units.

Maybe we're talking about two different standards here. I'm satisfied with all of the photos I publish in my gallery on Nikonians and on Photo.Net. Some photographers may feel that my published photos could have been even more sharply or more accurately focused, and maybe I should have expected a to get a higher percentage of keepers out of the cameras I use most often. I accept those arguments, especially if the degreee to which such photographers examine focus accuracy and sharpness is criticial to their photography enjoyment and satisfaction. For photographers with the latter approach, there may be a determined intent to always eke every last bit of accuracy from their chosen cameras and lenses. Can't argue with that either - the philosophy and the approach is perfectly sound.

The only thing I'm questioning is the use of test methods (not just yours - the commercial retail test kits are totally suspect IMO, for the reasons mentioned above) containing so many set up variables of lighting, ISO, chart positioning compromises, chart/target-to-camera-frame ratio, chart target point/edge size/dimension vs. camera focus sensor size and response characteristics, chart target point edge definition, horizontal/vertical/cross-type sensor differentiations, camera positioning, chart angle, sensor plane, lens choice, test result repeatability and so on. Then there's the inherent mechanical and optical variability of the particular AF system and chosen lenses which grossly affects testing result repeatability. Again, none of this information is new.

In fully controlled conditions, all I've ever been able to find is uncompensatable variability in an AF system with a given lens. The variability is only reflective of the tolerance range of the particular AF system design. High numbers of sample shots also reveal not only AF system variability but the variability of the lens mechanism as well.

Regression to the mean certainly says that sooner or later I'm going to be using a camera and lens combination which can benefit from AF fine tune. But I won't base a final decision on the results gleaned from tests done with a 45 degree target. Such targets are bascially compromises that are relatively easy to produce, package and sell. By contrast, setting up a series of absolutely parallel/plane targets in a home testing environment (on a parallel fore & aft rail system, with the camera mounted on a lateral positioning rail system), identical lighting for each target position, etc., etc., is expensive, space consuming, time consuming and usually highly impractical even for the most ardent hobbyists, enthusiasts and pros. And even if someone sets up such an elaborate testing system, a left-focus-sensor miscalibration such as that which occured in certain series of D800 bodies is still not remediable with the use of AF fine tune. That last part is a bit of a tangent - sorry.

The only time I've ever had to recalibrate any particular camera body and lens combination for focus accuracy is after the pair suffered damage on a research trip or from my own carelessness. Trip to Nikon Canada (in Mississauga, Ontario - just west of Toronto - very handy), payment of $250, and a perfect combination about 10 days later. A very rare occurence though because I try not to make a habit of dropping, hammering, banging around or abusing my gear. It happens anyway.

Somebody straighten me out on all this. I think Nikon added AF fine tune mainly as part of endless feature creep. I also know that several Nikonians have demonstrated successful AF fine tune testing and adjustments. But I also think the actual need for AF fine tune is so rare that the feature might as well not be there and that almost every Nikonian who has tackled AF fine tune (successfully or not) has had to battle the difficulties in focus target setup. At least one AF fine tune session (by a Nikon shooter who is local to me) resulted in a pin/tack/razor sharp zoom lens from 30-45mm but terrible results from 24-30mm and worse still from 45-70mm. If he had made the (I strongly believe) requisite number of shots sufficient to reveal the AF system variability in the camera/lens combo, he'd still have a very good zoom lens that (was) very sharp through its focal range. With that particular lens he was delighted with the improvement from 30-45mm because that's the focal range in which he spends most of his shooting time. But he rendered the rest of the lens' capabilities messed up. Seems counterproductive.

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bkinthebay

bkinthebay, BE
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#27. "RE: Third repair attempt fails" | In response to Reply # 26

bkinthebay Registered since 27th Feb 2010
Wed 30-Jan-13 06:29 PM


>It's easy to cause a mis-focus. A large percentage of the
>time, the focus point that a tester has positioned on a 45
>degree target sheet is not actually locking on at that chosen
>focus point. The camera may signal a confirmation (with the
>focus dot), but the resulting shot appears
>mis-/front-/back-focused because the lock signal was an
>approximation. This has been demonstrated many, many times in
>other threads on Nikonians - most or all of which predate your
>other thread on the subject. Nothing new here.

So you did not actually test the method I proposed yourself?

The whole idea of leaving *only* one dot visible when focusing is to eliminate the typical errors coming from targets placed at 45 degrees. Indeed, the rest of the target is here pure white and cannot contribute to the phase detection of the focusing system. This is easily confirmed by the total inability of the camera to focus if the collimator is not on the dot.

agitater

Toronto, CA
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#28. "RE: Third repair attempt fails" | In response to Reply # 27

agitater Gold Member Donor Ribbon awarded for his very generous support to the Fundraising Campaign 2014 Nikonian since 18th Jan 2007
Wed 30-Jan-13 07:44 PM | edited Wed 30-Jan-13 07:47 PM by agitater

>So you did not actually test the method I proposed yourself?

No - not yours. Many others though, including the commercial units I've reviewed.

>The whole idea of leaving *only* one dot visible when focusing
>is to eliminate the typical errors coming from targets placed
>at 45 degrees. Indeed, the rest of the target is here pure
>white and cannot contribute to the phase detection of the
>focusing system. This is easily confirmed by the total
>inability of the camera to focus if the collimator is not on
>the dot.

In my experience, cameras can sometimes assume focus, for a variety of reasons, when no normally obvious focus target is present. For example, in inconsistent lighting, the camera can sometimes read a faint shadow edge sufficiently well to attempt focus and allow the shutter to fire even when no obvious focus target is present on an ostensibly clean sheet of paper.

I'm not sure what you mean by the reference to a collimator. The hole in the top sheet which exposes the target is not a collimator - it's a mask. A collimator is particle modification device which is used to realign (collimate) a beam of particles (e.g., photons). A camera lens is a kind of collimator. Are you referring to the lens being used? If so, I'm missing your meaning.

An edge of the mask can also be a focus target as often as the target print itself. A flush or unflush far mask edge being grabbed hard (instead of the target because it's too small in the frame for the selected AF sensor) by the AF system, coupled with a lens that tends to focus slightly ahead, coupled with a camera AF system which focuses slightly ahead, may give a test result which looks spot on. There are all sorts of combinations of these three factors alone, which when coupled with 45 degree testing in particular, give photographers absolute fits of AF fine tune angst. To get a sense of what the camera is actually doing - not matter what testing metholdology is being used - the tester has to take a hundred photos or more just to chart the variability inherent in the particular camera and lens combination being tested.

I'm not trying to shoot down your efforts. I'm only injecting the important variables that I think should be fully accounted for in any AF focus testing system. The simplicity of your approach is genuinely attractive, but I don't see any way for it to be used, as-is, to produce accurate test results on a consistent basis. Then again, a 100-200 shot test series might produce enough variability data to make a judgement about AF fine tune. I just don't have the time to give your proposed test method a serious try, but I hope that someone else can.

What I'm suggesting though is that any testing at a 45 degree angle is difficult, at best, to do accurately. The angle in and of itself is a compromise solely for simplicity of test set up, but it materially challenges any camera's AF system in an inappropriate way. It's only ever been promoted by the producers of hobbyist AF testing kits because it's simple and small enough to fit into a manageable retail package. Angled test kits don't exist for any other reason. Parallel/plane target focus testing at various distances is generally a much more effectively accurate AF testing method, but it still requires more room and greater measurement accuracy to establish a parallel/plane relationship between camera sensor and target. It also generally produces more reliable results. Using your single target point by itself, in a parallel/plane test set up, would determine how effectively a cross-type sensor can accurately lock on to it. Maybe you've designed a target that is better than many of the others I've seen (noting too that some others still, have proven to be very good test targets no doubt). That last bit would be a real coup for you - seriously.

Once again, I'm not in any way criticising your goal of accurate AF testing and calibration, just any methodology which needlessly incorporates a 45 degree angle setup. To my way of thinking, the compromises and the test results are unacceptable.

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bkinthebay

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#29. "RE: Third repair attempt fails" | In response to Reply # 28

bkinthebay Registered since 27th Feb 2010
Wed 30-Jan-13 09:03 PM

>>So you did not actually test the method I proposed
>yourself?
>
>No - not yours. Many others though, including the commercial
>units I've reviewed.
>
>>The whole idea of leaving *only* one dot visible when
>focusing
>>is to eliminate the typical errors coming from targets
>placed
>>at 45 degrees. Indeed, the rest of the target is here
>pure
>>white and cannot contribute to the phase detection of the
>>focusing system. This is easily confirmed by the total
>>inability of the camera to focus if the collimator is not
>on
>>the dot.
>
>In my experience, cameras can sometimes assume focus, for a
>variety of reasons, when no normally obvious focus target is
>present. For example, in inconsistent lighting, the camera can
>sometimes read a faint shadow edge sufficiently well to
>attempt focus and allow the shutter to fire even when no
>obvious focus target is present on an ostensibly clean sheet
>of paper.
>

Sure it can happen. But only very occasionally does my camera fire when I aim it at a blank sheet of paper in focus priority mode. If it did more systematically, I would call this a bug in the focusing system.


>I'm not sure what you mean by the reference to a collimator.
>The hole in the top sheet which exposes the target is not a
>collimator - it's a mask. A collimator is particle
>modification device which is used to realign (collimate) a
>beam of particles (e.g., photons). A camera lens is a kind of
>collimator. Are you referring to the lens being used? If so,
>I'm missing your meaning.

Sorry for that; I used (AF) collimator as a synonym for AF point.

>
>An edge of the mask can also be a focus target as often as the
>target print itself. A flush or unflush far mask edge being
>grabbed hard (instead of the target because it's too small in
>the frame for the selected AF sensor) by the AF system,
>coupled with a lens that tends to focus slightly ahead,
>coupled with a camera AF system which focuses slightly ahead,
>may give a test result which looks spot on.

This is why you need to cleanly cut the hole as indicated. The focusing system analyses all the information available. A badly cut edge would provide some at a different place than intended.
On the other hand, the hole should be small compared to the expected depth of field to analyse the resulting pattern when the dotted paper is exposed. Typically, it should appear of similar size as the AF point in the viewfinder. If the camera focuses on the front of the dot or its back as a result of the cut out, it does not make a difference.

>There are all
>sorts of combinations of these three factors alone, which when
>coupled with 45 degree testing in particular, give
>photographers absolute fits of AF fine tune angst. To get a
>sense of what the camera is actually doing - not matter what
>testing metholdology is being used - the tester has to take a
>hundred photos or more just to chart the variability inherent
>in the particular camera and lens combination being tested.
>
>

On this one you will have to trust me if you don't find the need to try out: I took hundreds of photo to play with all my lenses, and the variability is negligible compared to the size of the sharp zone of dots you have to observe on the target. I therefore strongly believe that the camera (D800) is very systematic at picking the dot consistently when there is nothing else around it except white paper. I think most if not all of the variability usually observed with other methods comes from the fact that the target has several parts at different distances (especially a ruler aimed at 45 degrees) that are picked a bit randomly if they are too close.

>I'm not trying to shoot down your efforts. I'm only injecting
>the important variables that I think should be fully accounted
>for in any AF focus testing system. The simplicity of your
>approach is genuinely attractive, but I don't see any way for
>it to be used, as-is, to produce accurate test results on a
>consistent basis. Then again, a 100-200 shot test series might
>produce enough variability data to make a judgement about AF
>fine tune. I just don't have the time to give your proposed
>test method a serious try, but I hope that someone else can.
>
>What I'm suggesting though is that any testing at a 45 degree
>angle is difficult, at best, to do accurately. The angle in
>and of itself is a compromise solely for simplicity of test
>set up, but it materially challenges any camera's AF system in
>an inappropriate way. It's only ever been promoted by the
>producers of hobbyist AF testing kits because it's simple and
>small enough to fit into a manageable retail package. Angled
>test kits don't exist for any other reason. Parallel/plane
>target focus testing at various distances is generally a much
>more effectively accurate AF testing method, but it still
>requires more room and greater measurement accuracy to
>establish a parallel/plane relationship between camera sensor
>and target. It also generally produces more reliable results.
>Using your single target point by itself, in a parallel/plane
>test set up, would determine how effectively a cross-type
>sensor can accurately lock on to it. Maybe you've designed a
>target that is better than many of the others I've seen
>(noting too that some others still, have proven to be very
>good test targets no doubt). That last bit would be a real
>coup for you - seriously.
>
>Once again, I'm not in any way criticising your goal of
>accurate AF testing and calibration, just any methodology
>which needlessly incorporates a 45 degree angle setup. To my
>way of thinking, the compromises and the test results are
>unacceptable.
>
I totally agree with you that one has to get rid of the problems generated by aiming at a target at 45 degrees. What I am claiming is that by exposing only one dark dot on the target when focusing, you are not aiming at 45 degrees or any other angle. With only a small dot to aim at, there is no reference to any direction. It's just like looking at a point floating in the air.

I welcome constructive critism about the methodology proposed. In fact, I share absolutely all the objections you raise about using targets aimed at an angle (there is a lot of randomness in the sample pictures taken). It is precisely because of them that I started to think about an alternative that still offered a view of where the acquired focus point lies in terms of front or back focusing. What I am saying is that if you only give the focusing system one dot to analyse, variability is negligible in practice (at least with my camera and objectives). And honestly, if my camera was not able to pick consistently such an easy target, I would not felicitate Nikon .

agitater

Toronto, CA
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#30. "RE: Third repair attempt fails" | In response to Reply # 29

agitater Gold Member Donor Ribbon awarded for his very generous support to the Fundraising Campaign 2014 Nikonian since 18th Jan 2007
Thu 31-Jan-13 03:57 PM

>On this one you will have to trust me if you don't find the
>need to try out: I took hundreds of photo to play with all my
>lenses, and the variability is negligible compared to the size
>of the sharp zone of dots you have to observe on the target. I
>therefore strongly believe that the camera (D800) is very
>systematic at picking the dot consistently when there is
>nothing else around it except white paper. I think most if not
>all of the variability usually observed with other methods
>comes from the fact that the target has several parts at
>different distances (especially a ruler aimed at 45 degrees)
>that are picked a bit randomly if they are too close.

I think you've touched on a more important matter. Making it, hypothetically, so easy for the camera to lock focus (by eliminating the potential distraction of adjacent potential targets) doesn't really test the accuracy or acuity of the camera's AF system. In actual photography situations, a chosen AF target or subject is almost always surrounded by nearby potential targets. So it's important, during any sort of AF system testing I think, to create a test bed that in several important respects challenges the camera's AF system as a whole rather than just a single AF sensor.

>I totally agree with you that one has to get rid of the
>problems generated by aiming at a target at 45 degrees. What I
>am claiming is that by exposing only one dark dot on the
>target when focusing, you are not aiming at 45 degrees or any
>other angle. With only a small dot to aim at, there is no
>reference to any direction. It's just like looking at a point
>floating in the air.

The problem I have with your methodology is that it is an approach which shows mainly that the method can work, rather than an approach which challenges the overall accuracy of the camera's AF system.

>What I am saying is that if you
>only give the focusing system one dot to analyse, variability
>is negligible in practice (at least with my camera and
>objectives). And honestly, if my camera was not able to pick
>consistently such an easy target, I would not felicitate Nikon
> .

Again, my feeling is that testing of an AF system using a method which does not challenge the entire AF system at once, does not provide a result or a basis for AF fine tune adjustment which will be viable in real shooting conditions in which, invariably, the entire AF system is always challenged. By eliminating proximal targets, you may only be demonstrating whether or not the chosen AF sensor point placed on your target actually functions, not how accurate that AF sensor point actually is. I suggest the reason is that the both contrast detection and phase detection use a variety of information proximal to the AF target to make presumably accurate decisions about the viability of the chosen target point and how effectively in can be locked on. Without proximal information (literally, contrast or phase information adjacent to the selected AF target), I don't think the AF system is actually being effectively tested.

Rather than eliminating some test bench variables with your methodology, I think instead the methodology reduces the ability to accurately determine the state of actual AF system calibration.

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bkinthebay

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#31. "RE: Third repair attempt fails" | In response to Reply # 30

bkinthebay Registered since 27th Feb 2010
Thu 31-Jan-13 04:33 PM

The methodology is not about testing the efficiency of the whole AF system in real life situations. It is about testing wether or not, on the simplest possible target, phase detection produces front or back focusing.

If the camera is not successful at properly focusing such a target, it's a clear sign there is a problem. You cannot hope to get good results in real life situations like you describe if the camera cannot even handle ideal conditions. It's just step zero in the troubleshooting strategy.

Here is what I would recommend to people about the whole fine tuning business:

1) Just use your camera without worrying about it. If you get a high percentage of pictures in focus, everything is fine. No need to shoot targets. Out of focus images will happen, no system is 100% accurate and the number of bad images will decrease as you will gauge better how you system behaves.

2) If you systematically get out of focus images, it is either you that has poor technique or your camera needs to be checked. If you think your technique is proper, then try a method such as the one I propose. If your camera systematically misses this straightforward target, your autofocus system is not well calibrated and you should consider fine tuning it by analysing the test pattern on the dotted chart. Then go back to real life photos and see if things have improved. The method has no other pretension.



agitater

Toronto, CA
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#32. "RE: Third repair attempt fails" | In response to Reply # 31

agitater Gold Member Donor Ribbon awarded for his very generous support to the Fundraising Campaign 2014 Nikonian since 18th Jan 2007
Thu 31-Jan-13 05:03 PM

>The methodology is not about testing the efficiency of the
>whole AF system in real life situations. It is about testing
>wether or not, on the simplest possible target, phase
>detection produces front or back focusing.

I understand your approach. What I'm suggesting is that I believe the simplification is largely counterproductive because I think it inherently prevents the chosen sensor (which is part of a larger system) from functioning most effectively (as a fundamental part of the larger system) for the application dictated by your methodology. Some AF system experts should chime in here I think.

>If the camera is not successful at properly focusing such a
>target, it's a clear sign there is a problem. You cannot hope
>to get good results in real life situations like you describe
>if the camera cannot even handle ideal conditions. It's just
>step zero in the troubleshooting strategy.

My point is that the condition you set up in your methodology is not in fact ideal. I believe that isolating a target to provide, effectively, a single data registration point for the AF system, does not reflect the engineering or software design approach of the AF system. The AF system is designed to work best, as I understand it, when provided with significantly more target and proximal data than is provided when using your method.

>Here is what I would recommend to people about the whole fine
>tuning business:
>
>1) Just use your camera without worrying about it. If you get
>a high percentage of pictures in focus, everything is fine. No
>need to shoot targets. Out of focus images will happen, no
>system is 100% accurate and the number of bad images will
>decrease as you will gauge better how you system behaves.

Well said.

>2) If you systematically get out of focus images, it is either
>you that has poor technique or your camera needs to be
>checked.

Very well said again.

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johno

St. Louis, US
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#33. "RE: Third repair attempt fails" | In response to Reply # 25

johno Silver Member Nikonian since 23rd May 2006
Thu 31-Jan-13 05:22 PM

>>Unfortunately, it seems that they are unable or unwilling
>to read my
>>letter explaining what the fault is.
>
>I had the same experience. My explanation of a problem with
>flash commander mode was condensed to "flash doesn't
>work" in the service order. Nikon replaced my camera the
>fourth time I sent it for repair.

Of course this results in the tech who gets the camera testing it and finding out the flash does in fact work, and back it goes into your hands.

Did your replacement camera work OK?

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bkinthebay

bkinthebay, BE
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#34. "RE: Third repair attempt fails" | In response to Reply # 32

bkinthebay Registered since 27th Feb 2010
Thu 31-Jan-13 05:31 PM

>>The methodology is not about testing the efficiency of
>the
>>whole AF system in real life situations. It is about
>testing
>>wether or not, on the simplest possible target, phase
>>detection produces front or back focusing.
>
>I understand your approach. What I'm suggesting is that I
>believe the simplification is largely counterproductive
>because I think it inherently prevents the chosen sensor
>(which is part of a larger system) from functioning most
>effectively (as a fundamental part of the larger system) for
>the application dictated by your methodology. Some AF system
>experts should chime in here I think.
>
>>If the camera is not successful at properly focusing such
>a
>>target, it's a clear sign there is a problem. You cannot
>hope
>>to get good results in real life situations like you
>describe
>>if the camera cannot even handle ideal conditions. It's
>just
>>step zero in the troubleshooting strategy.
>
>My point is that the condition you set up in your methodology
>is not in fact ideal. I believe that isolating a target to
>provide, effectively, a single data registration point for the
>AF system, does not reflect the engineering or software design
>approach of the AF system. The AF system is designed to work
>best, as I understand it, when provided with significantly
>more target and proximal data than is provided when using your
>method.
>

This is indeed a concern I initially had. However, when using one AF point, I have observed in my case that if the lenses are well calibrated with the target, they are also fine in real life. However, without knowing how the algorithm is actually designed, this statement is only based on personal observations with my specific equipment...

agitater

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#35. "RE: Third repair attempt fails" | In response to Reply # 34

agitater Gold Member Donor Ribbon awarded for his very generous support to the Fundraising Campaign 2014 Nikonian since 18th Jan 2007
Thu 31-Jan-13 07:18 PM

>This is indeed a concern I initially had. However, when using
>one AF point, I have observed in my case that if the lenses
>are well calibrated with the target, they are also fine in
>real life. However, without knowing how the algorithm is
>actually designed, this statement is only based on personal
>observations with my specific equipment...

I think you've boiled it down to the essential point of luctation. I think you've made an excellent proposition for the basis of a comparison between competing AF testing methodologies as they exist in places other than fully equipped test labs. I wish I had the time to write a spec and then do the comparative testing.

Thank you for the discussion.

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rplst8

Johnstown, US
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#36. "RE: Third repair attempt fails" | In response to Reply # 32

rplst8 Silver Member Nikonian since 18th Dec 2008
Fri 01-Feb-13 01:18 PM

>>The methodology is not about testing the efficiency of
>the
>>whole AF system in real life situations. It is about
>testing
>>wether or not, on the simplest possible target, phase
>>detection produces front or back focusing.
>
>I understand your approach. What I'm suggesting is that I
>believe the simplification is largely counterproductive
>because I think it inherently prevents the chosen sensor
>(which is part of a larger system) from functioning most
>effectively (as a fundamental part of the larger system) for
>the application dictated by your methodology. Some AF system
>experts should chime in here I think.
>
>>If the camera is not successful at properly focusing such
>a
>>target, it's a clear sign there is a problem. You cannot
>hope
>>to get good results in real life situations like you
>describe
>>if the camera cannot even handle ideal conditions. It's
>just
>>step zero in the troubleshooting strategy.
>
>My point is that the condition you set up in your methodology
>is not in fact ideal. I believe that isolating a target to
>provide, effectively, a single data registration point for the
>AF system, does not reflect the engineering or software design
>approach of the AF system. The AF system is designed to work
>best, as I understand it, when provided with significantly
>more target and proximal data than is provided when using your
>method.

This is only true in the multi-point AF modes. In single-servo, single-point AF the only data that is important is that which is under the selected focus point. If the camera can not perform well in this mode on a target with good contrast (in the proper plane), there is no reason to believe it would perform well in "real-world" situations.

While the camera may achieve better results on still subjects using single-servo, dynamic-area or continuous-servo, dynamc-area or 3D-tracking when the single-servo, single-point results are poor, this is completely beside the point.

If all of the focus points did work well in single-servo, single-point, I would bet a lot of money that the performance in continous-servo and dynamic-area modes would improve greatly.

IMO it's a ignoratio elenchi to say "yes AF-S single-point doesn't work well in test scenarios, use AF-C dynamic-area in the real-world."

--
RL

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agitater

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#37. "RE: Third repair attempt fails" | In response to Reply # 36

agitater Gold Member Donor Ribbon awarded for his very generous support to the Fundraising Campaign 2014 Nikonian since 18th Jan 2007
Fri 01-Feb-13 02:36 PM

>This is only true in the multi-point AF modes. In
>single-servo, single-point AF the only data that is important
>is that which is under the selected focus point.

If you're basing your comment on factual technical knowledge about the way in which the AF system works, then you've just added some really valuable information. The thing is, I don't have precise technical knowledge about the AF system and I've been making an assumption that even using a single point AF mode it is still necessary for the AF system to use proximal data in order to get the best possible focus lock.

>If all of the focus points did work well in single-servo,
>single-point, I would bet a lot of money that the performance
>in continous-servo and dynamic-area modes would improve
>greatly.

I agree, and it seems self-evident. My own point has been that the proposed test method doesn't allow the AF system's single point mode to work to all of its strengths.

>IMO it's a ignoratio elenchi to say "yes AF-S
>single-point doesn't work well in test scenarios, use AF-C
>dynamic-area in the real-world."

I suggest that it is not a good idea to critique grammar, sentence construction and so on in a public forum. Irrelevant conclusion (ignoratio elenchi) or not, I'd ask for a clarification. For example, although throughout this part of the thread the posters have been careful about noting that they are expressing opinion and supposition and the results of experiment, you state unqualifyingly that "In single-servo, single-point AF the only data that is important is that which is under the selected focus point" but don't offer any technical information in support. So your statement might be judged merely reductio ad absurdum (proof by contradiction). Help us by explaining your understanding that Nikon's AF system does not use or does not necessarily need proximal data when it is set to use a single AF point. Believe me, I need the education.

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rplst8

Johnstown, US
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#38. "RE: Third repair attempt fails" | In response to Reply # 37

rplst8 Silver Member Nikonian since 18th Dec 2008
Fri 01-Feb-13 05:14 PM

>>This is only true in the multi-point AF modes. In
>>single-servo, single-point AF the only data that is
>important
>>is that which is under the selected focus point.
>
>If you're basing your comment on factual technical knowledge
>about the way in which the AF system works, then you've just
>added some really valuable information. The thing is, I don't
>have precise technical knowledge about the AF system and I've
>been making an assumption that even using a single point AF
>mode it is still necessary for the AF system to use proximal
>data in order to get the best possible focus lock.
>
>>If all of the focus points did work well in single-servo,
>>single-point, I would bet a lot of money that the
>performance
>>in continous-servo and dynamic-area modes would improve
>>greatly.
>
>I agree, and it seems self-evident. My own point has been that
>the proposed test method doesn't allow the AF system's single
>point mode to work to all of its strengths.
>
>>IMO it's a ignoratio elenchi to say "yes AF-S
>>single-point doesn't work well in test scenarios, use
>AF-C
>>dynamic-area in the real-world."
>
>I suggest that it is not a good idea to critique grammar,
>sentence construction and so on in a public forum. Irrelevant
>conclusion (ignoratio elenchi) or not, I'd ask for a
>clarification. For example, although throughout this part of
>the thread the posters have been careful about noting that
>they are expressing opinion and supposition and the results of
>experiment, you state unqualifyingly that "In
>single-servo, single-point AF the only data that is important
>is that which is under the selected focus point" but
>don't offer any technical information in support. So your
>statement might be judged merely reductio ad absurdum (proof
>by contradiction). Help us by explaining your understanding
>that Nikon's AF system does not use or does not necessarily
>need proximal data when it is set to use a single AF point.
>Believe me, I need the education.
>

Please don't misunderstand; I wasn't critiquing your grammar at all.

That said; assume for a second that in the single-servo, single-point mode the camera uses information from the nearby focus points. The designer of the algorithm could not assume anything about the shape of the object being focused on, and would therefore be hard pressed to use this data in any useful way. For instance, am I focusing on a brick wall or someone's nose? It could very well be that given the aperture, focal length, subject size, and distance that the selected focus point falls on someone’s nose, while the neighboring ones fall on their cheeks/eyes and are out of focus.

Therefore, based on logical reasoning like this and Nikon's description of the single-point mode (while in single-servo) I find it very unlikely that it uses nearby focus points in this mode. Simply put, this mode is trying to minimize the phase error measured between the two microlenses and sensors that make up the selected focus point.

--
RL

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agitater

Toronto, CA
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#39. "RE: Third repair attempt fails" | In response to Reply # 38

agitater Gold Member Donor Ribbon awarded for his very generous support to the Fundraising Campaign 2014 Nikonian since 18th Jan 2007
Fri 01-Feb-13 10:20 PM


>Please don't misunderstand; I wasn't critiquing your grammar
>at all.

I know. The referenced quote wasn't mine. No worries.

>That said; assume for a second that in the single-servo,
>single-point mode the camera uses information from the nearby
>focus points. The designer of the algorithm could not assume
>anything about the shape of the object being focused on, and
>would therefore be hard pressed to use this data in any useful
>way. For instance, am I focusing on a brick wall or someone's
>nose? It could very well be that given the aperture, focal
>length, subject size, and distance that the selected focus
>point falls on someone’s nose, while the neighboring ones fall
>on their cheeks/eyes and are out of focus.

It's my understanding that in a contrast detection AF system (which I believe measures intensity differential of adjacent pixels in a detected field), the AF sensor field is swept to detect the point of highest contrast relative to the selected AF target. It seems then that Bernard's test methodology would be very troublesome for a contrast detection AF system mainly because the system has to use a large enough sample from the field sweep to both confirm the target and detect sufficient intensity differential samples to lock focus.

In a phase detect AF target test, with the camera in AF-S mode and using the center cross-type sensor, the aperture has to be large enough to ensure that both the vertical and horizontal detection strips have enough light to operate to spec and - again, only as I understand the engineering - there has to be a sufficiently wide phase differential detected adjacent to the selected AF target in order for the selected AF sensor point to gain a reliably consistent lock on the presumably smaller phase differential under the chosen AF sensor point.

That's my basis for wondering if the methodology suggested by Bernard can actually produce results reliable enough for AF fine tune adjustments. If my understanding of the AF system engineering and functionality is incorrect, then I'm probably wrong. So I'd really like it if an AF system expert chimed in here and either confirmed my suspicions or straightened me out.

>Therefore, based on logical reasoning like this and Nikon's
>description of the single-point mode (while in single-servo) I
>find it very unlikely that it uses nearby focus points in this
>mode. Simply put, this mode is trying to minimize the phase
>error measured between the two microlenses and sensors that
>make up the selected focus point.

I'm contending that your reasoning doesn't match the way in which the AF-S phase detect AF system functions, but now I'm also not as sure about my own reasoning as I was before. I've really got to find some time to dig up the technical specs on the various AF systems out there. I realize my opinions are questionable because I don't have enough technical knowledge about the system.

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Howard Carson

Vox Sciurorum

Newton, US
240 posts

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#40. "RE: Third repair attempt fails" | In response to Reply # 33

Vox Sciurorum Registered since 18th Oct 2007
Fri 01-Feb-13 11:13 PM

>>>Unfortunately, it seems that they are unable or
>unwilling
>>to read my
>>>letter explaining what the fault is.
>>
>>I had the same experience. My explanation of a problem
>with
>>flash commander mode was condensed to "flash doesn't
>>work" in the service order. Nikon replaced my camera
>the
>>fourth time I sent it for repair.
>
>Of course this results in the tech who gets the camera testing
>it and finding out the flash does in fact work, and back it
>goes into your hands.
>
>Did your replacement camera work OK?

My replacement works so far. I haven't taken a lot of shots with remote flash.

Vlad_IT

US
1354 posts

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#41. "RE: Third repair attempt fails" | In response to Reply # 1

Vlad_IT Silver Member Nikonian since 21st Sep 2011
Mon 26-Aug-13 02:37 AM

>I have read in several places that Nikon would replace a
>camera or lens after 3 failed repair attempts, but you won't
>find any official statement from Nikon to that effect, and
>there is surely always some discretion.
>


In the USA it's called Lemon Law and any company must replace the product if that product required three repairs during warranty period. OP just need to request for a new (it will be a refurbished) camera.

Best regards,
Vlad

G