Photokina 2012: Nikon talks about the D800's outer AF issue

"I AM here4U" at Photokina 2012

Note: A copy of this blog article has been published in German language too. Please refer to the corresponding version (Deutsch) before posting comments. Thank You.

Prior to Photokina, I had scheduled a meeting with Nikon Germany, partly in order to discuss the known issue regarding the outer AF focus fields of the Nikon D800 camera.

So, on Tuesday I had the pleasure to discuss the topic extensively with both Michael Wollburg (Manager Customer Support Nikon GmbH) and a Nikon technician in charge. The meeting was very friendly and constructive.


Below, I am going to disclose my impressions which may differ from the original wording of what has been said (I have been there as member of accredited press; but I did not opt for an interview; I rather wanted to learn the bare facts). Therefore, any mistakes in the remainder are only my fault. Now for the infos:

• Nikon has acknowledged, found and understood the root cause of the issue. It has been eliminated in the current production (however, I guess we'll never know when and from which serial numbers on).
• The root cause is a misalignment of the AF module when mounted, outside of Nikon's own production tolerances. But be asserted we are still talking micro meters here ...
• The issue for affected D800 can be solved in selected Nikon service centers; such as Düsseldorf, Germany.
• The procedure is currently rolled out to more Nikon service centers.
• The fixing procedure for Nikon is a tedious one. It includes writing individual calibration values into the firmware. For larger deviations, the AF module will first mechanically be re-aligned. This may actually include the AF auxiliary mirror in some cases.
• This method is believed to deliver an autofocus precision which is at least as good as of cameras from a fresh batch. I could not clarify if there is a chance for both methods being non-equivalent in some way. However, Nikon Germany does not think so. They rather wholeheartedly believe that the in-service calibration procedure resolves the issue as good as current production does, if not better.
• There is some dispute about the eventual success of the service measures from Nikon so far. Not only are there differences between countries and early attempts have faced difficulties and a lack of a clear procedure. But there is additional uncertainty about what to reasonably expect, esp. with the large sensor resolution of the D800. Therefore, the eventual success of the service measures from Nikon must be gauged relative to what is feasible technically. Every AF module from every vendor has finite AF field deviations. Lumolabs determined (depending on the lens too) deviations of up to 40µm between AF fields (cf. www.falklumo.com/lumolabs/articles/D800Focus/SensorArray.html) as being usual in the market and acceptable for good image quality where 20µm would be very good. Such are accuracy values as found in other cameras (e.g., D3). According to Nikon, we shall expect the same (or better) for freshly produced batches of D800 from Nikon, or for D800 now being calibrated in service. LumoLabs intends to verify this claim. Until then, we cannot really know if isolated continued reports about inacceptable AF accuracy after service are due to a failure during calibration or an unreasonable expectation. It is this blog which actually proposed a method to distinguidh between the two. Nikon is supporting our contribution to bring the discussion back to facts.
• Nikon does actually not know how many D800 of the early batches have been affected. Despite all oddities, the so-called service-rate of the D800 is unremarkable and only "sligthly increased" (compared to other camera models).
• I take it that Nikon will not publish an official statement about this issue. And I take it too that meanwhile this has been internally decided in Japan. So, don't ask for it ... ;)
• Independently of corporate information policy, Nikon wants to help all customers with the problem without asking much questions. This includes returned goods from dealers and service calls after expiration of the warranty period. (Note however, that Nikon Germany cannot speak for the rest of the world.)
• I do now actually recommend affected D800 photographers, to contact Nikon or their dealer i order to schedule an AF calibration job done on it.
• Personally, I do think it is a very good idea to additionally create an A2C2 chart (before and after). This should help your camera's resale value too.

By the way, Nikon Germany has internally forwarded both our LumoLabs white papers and even had a closer look at FoCal. The AFMA unit step values we determined (approx. 4µm at f/2.8) have been received as plausible and it seems to be an accepted fact within Nikon that AFMA unit step values do indeed depend on a lens' nominal aperture.

It will be possible to check Nikon's claims (resolution of the AF issue both in service (normally) and current production) by using our testing methodology. If claims turn out to be true (as to be expected) then I think the entire AF field problem issue can settle. Slowly. But nevertheless make me make a clear call towards Nikon Japan: With your current information policy (or lack thereof) you are heading towards difficult times. I AM HERE FOR YOU ...

Falk

Further reading:
LumoLabs: Nikon D800/E outer AF sensor accuracy (First blog article)
LumoLabs: Using FoCal for testing of an AF sensor array (Second blog article)