There has been quite a bit of buzz around the Nikon D800 / D800E focusing issues and one of the most recurring topics of discussions seems to be around the asymmetric focus issue (left AF focus issue). As I have already explained in my “how phase detection autofocus works” article, any DSLR is prone to having AF issues, simply because of the way the phase detect sensor works.
Folks that have been shooting with DSLRs for years and have gone through different camera bodies know very well that every camera announced to date had a small number of defective units out there. Some had rare issues that required service or replacement, others had defective components (such as battery) that had to be recalled and some units were plagued with autofocus calibration issues. In the big picture, however, the number of truly affected units was very small. The Nikon D7000 DSLR, for example, received some negative feedback specifically on its autofocus problems. After doing some extensive research and gathering lots of data from our readers, it turned out to be that most problems I looked at were user-related issues and very few units actually had manufacturing defects. Negative feedback is always more popular and when someone complains about a rather serious problem, it quickly gets blown up. Most people don’t even bother providing positive feedback anyway, so all the bad stuff gets surfaced rather quickly. Also, when looking through customer feedback before buying a product, have you noticed that you typically tend to look for negative feedback more than positive? There is a simple explanation for this type of behavior – people would rather read about product issues to understand limitations and potential problems, than only look at rave reviews.
Does this mean that all the talk around the Nikon D800 / D800E is unjustified and biased? The typical phase detect autofocus problems we have been seeing ever since the first DSLR camera out are there in a small number of units (probably no more than 5%), which is pretty normal, given that autofocus components could shift even during the transportation process. However, the Asymmetric Focus Issue that we have been hearing about lately is a Nikon D800-specific problem. And it seems like many Nikon D800 / D800E units are affected by this specific problem.
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Is the issue confirmed?
I have been gathering as much data as possible, similar to what I have done with the D7000 to understand how many units are affected and to see if I can identify the root cause of the problem. After several phone calls to Nikon Service when the issue first popped up, I quickly realized that Nikon Japan went silent on the issue internally – pretty much none of the service personnel knew anything about the asymmetric focus issue. Many of us that sent their D800 cameras initially to Nikon Service ended up getting their units back without any adjustments, with notes suggesting that the camera operates within factory norms. In short, most Nikon service personnel had no idea how to address the issue and they mostly blamed end users for improperly testing their equipment. I could understand how that would make sense with Nikon D7000 owners, many of whom were first time DSLR buyers. However, many Nikon D800 owners are long time shooters that either upgraded from a DX body, upgraded from a full-frame body or switched from Canon – people with some good photography experience that know what they are doing. So it was a matter of time until persistence won and Nikon Service was provided with proof that the issue indeed exists in many units sold to date. Nikon Service was able to replicate autofocus issues on multiple occasions (confirming issues on individual service basis only) and within a few months they came up with a permanent fix. Instructions on how to service affected units were quickly distributed internally and Nikon has been fixing affected D800/D800E units using these instructions ever since (see more on this below).
My next goal was to see how many units are truly affected. While it looks like only a batch of the D800 / D800E units is affected with the AF issue, I am actually finding the numbers to be pretty big. As many as half of the units that I have tested and received reports on thus far have a very noticeable asymmetric AF problem on the left side. To me it looks like very few units do not have a problem – most have very noticeable to somewhat noticeable focus errors. So as far I am concerned, I can confirm that the asymmetric focus issue indeed does exist on many D800 DSLRs cameras. However, NPS, Nikon USA and Nikon Japan have not issued any official statements about this and I doubt they will.
What Caused the D800/D800E Asymmetric Focus Issue
What is the reason for the asymmetric focus / left AF point issue? Why does the center and right focus points work fine and the left focus point does not? There is a lot of debate around the cause of the asymmetric focus issue. Unfortunately, very few people at Nikon know the actual cause and they are not eager to share. I have also phoned some people up that have direct relationships with Nikon to see if they can get an answer. As you might have guessed, everyone decided to keep their mouths shut on this issue. It has been tough to get anyone to say anything, but the service engineers at Nikon have been quite helpful in providing as much intelligence as possible and sharing their insights on the situation.
Here is my conclusion based on the intelligence and comments I have received from the service folks at Nikon (I won’t mention any names here). The main cause seems to be with the testing/QA phase of the manufacturing process.
When the phase detect sensor, along with the main and secondary mirrors are installed and properly aligned/angled on the camera (as explained in detail in my “how phase detection autofocus works” article), the setup goes through some rigorous computerized calibration process, during which any potential offsets that happened during the manufacturing process must be compensated. Basically, it is a process similar to AF Fine Tune, except it is done on each focus point individually. Since the manufacturing process is not perfect and even computer calibrated manufacturing processes will have a certain delta to precision, manufacturers set certain thresholds on these measurements. The phase detect sensor could be angled slightly differently on any or all sides. The same thing with the primary and secondary mirrors, which could be off and angled wrong. This deviation could be very small, smaller than a millimeter and it could cause a lot of serious AF grief. Recognizing that adjusting the yaw and pitch of the phase detect sensor or continuously trying to tweak the angle of the main and secondary mirrors is not always viable, Nikon developed a system, where it uses computerized tools and software to compute and compensate for these differences. Once those differences on each focus point are identified, a computer program writes the adjusted values into the permanent camera memory (Flash ROM).
So with all these computerized tests, how could Nikon could have produced a left AF issue? It seems like it was the testing setup that was off. Nikon relies on a special “autofocus calibration” rig when doing this tuning and something shifted the left targets by a little. It might have been the earthquake or improper adjustment by a technician. Either way, whichever units went through this setup eventually ended up with an AF issue.
So far this seems to be the most agreed theory behind the asymmetric focus issue.
What Nikon Service Centers are doing
By now you might be wondering what Nikon is doing to address the autofocus problem when you send it for repair. There seems to be a lot of confusion about what is done to the camera – from turning a simple hex wrench inside the camera chamber to fully automated calibration using computer software, so I wanted to provide some insight into the actual process. Please keep in mind that the below information is not officially released by Nikon (and probably never will be). It is based on the information Nikon service personnel have provided to us over the phone when repairing a Nikon D800 with an AF issue.
Some of our readers have sent me some information on manual calibration of the secondary mirror with a hex wrench (eccentric pin close to the sensor), saying that it helped with resolving AF problems. While a wrong angle can certainly cause AF issues, I would not try to adjust any mirrors in a DSLR, especially if your autofocus is way off. A couple of turns of the hex wrench could completely shift your focus points and give you plenty of other headache. In addition, if the angle is wrong, you could end up with a tilted setup, where the top of the frame will always differ than the center and the bottom. Don’t do that – even Nikon Service rarely touches these pins!
The D800 calibration process for the left AF issue is actually a pretty straightforward process, according to what Nikon service technicians told me (as long as the mirror angles are good). They mount your camera to a calibration rig comprised of test charts for each AF point, then use precision software to re-calibrate your camera (similar to what Nikon does during the QA phase of the production process). Calibration is typically done with a Nikon 50mm f/1.4D lens, but other lenses such as the Nikon 24-70mm f/2.8G are also available for testing. The whole process can be done in less than an hour, often with other adjustment checks, sensor cleaning, etc. Once the recalibration is done and new AF values have been identified, they are permanently written into the camera ROM.
So if you send your camera to a service center, they should be able to fix the issue pretty quickly. The only exception is when there is a serious AF focus problem (not just left AF) – if software compensation does not work, the camera has to be disassembled and manual yaw and pitch adjustments have to be carried out. That process is very painful and could take hours to complete…
The usefulness of AF Fine Tune
After I posted my last article on “how to quickly test your DSLR for autofocus issues“, I received a few emails and comments from our readers, asking why I did not talk about AF Fine Tune as a way to try to resolve camera AF issues. I specifically held off on that piece for two reasons – first, because AF Fine Tune is not always helpful, especially when using very high values above 10 (more on this later) and second, because AF Fine Tune often does not address camera AF problems. The Nikon D800E that I received has a really nasty case of AF problem that requires a minimum of -20 to work right with my lenses. Why should I have to retest and readjust all my lenses, if the problem is clearly with the camera?
Official statement from Nikon
Given how many people are going through this asymmetric focus issue, you would expect Nikon to recognize the problem and take care of it right? As consumers, we are quite used to seeing occasional product recalls and when a product has a manufacturing defect, we expect the manufacturer to issue a statement and take care of the issue. Failure can be forgiven, as long as the manufacturer pleads guilty and takes corrective action. However, the Japanese culture is the exact opposite – failure is both unacceptable and shameful. As we have seen with the whole Toyota Prius fiasco, accepting a failure is typically the last resort for the Japanese. They would rather go silent, than say they are sorry and take care of the problem. And it is not just Japanese that do this – many other countries and cultures are quite similar in that regard.
With this mentality, I doubt we will see an official statement from Nikon on this issue. If more and more people discover the problem, which I think many are simply ignoring, and escalate it to Nikon, we might get something out of them. Otherwise, it will be just another issue that will be forgotten over time. Nikon will fix its production fault (and it probably already has by now), so future batches will get less and less complaints, but I do not see how they could deal with this any other way. Issuing an official statement would not only hurt the company’s image and add bad publicity, but it would also most likely require a product recall, which is a very expensive process as you may already know.