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D800 Autofocus issues II

Started Jan 25, 2014 | Discussions thread
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Re: The absence of evidence is not evidence of absence
In reply to Simon Garrett, Jan 29, 2014

Simon Garrett wrote:

fPrime wrote:

Simon Garrett wrote:

We know there was a left-focus issue with early D800s (now long-since fixed), and I'm sure any particular D800 might have a manufacturing defect (or have broken).

Left AF fixed? That's a bit assumptive given the problem continues to be reported to Amazon in units sold as late as Q4 2013. It's even more troubling because not everyone rigorously tests their camera for focus accuracy upon receipt nor do most enthusiasts have the fast primes with shallow DOF required to detect the Left AF issue. If anything, the anecdotal evidence suggests that the Left AF problem persists and is not identified by Nikon's internal QC. See just one example:

Soooo many 5 stars - Did I get a lemon?, October 14, 2013

By Nelson - See all my reviews Amazon Verified Purchase(What's this?) This review is from: Nikon D800 36.3 MP CMOS FX-Format Digital SLR Camera (Body Only) (Electronics) I'll not spend too much time on this review because most problems I got has already been extensively written in here. Since on its release the D800 had the soft focus issue, I waited until now to buy it in the hope the bug had been fixed. I got the camera on Sep 15, 2013 and on the first pictures I noticed right away the bad soft left focus. Not sure about this one, so take with a grain of salt, the liveview mode apparently accentuate the soft focus issue.

I think we'd need a bit more information before regarding this as evidence. Sounds more like he hadn't got used to the camera (he's talking about his first pictures), or even buyer's remorse. Did he come back and post after more considered and detailed analysis, I wonder?

No need to wonder, Simon, look at the ensuing dialogue for yourself on Amazon. Then look at the numerous other 1 and 2 star reviews of the D800 from 2013, most are centered around focus. It's not like the user above was the one Left AF report from last year.

Either someone has evidence of a generic focus issue with the D800, or it's reasonable to assume that there isn't any generic issue. Just as it's reasonable to assume that D800s don't spontaneously morph into candyfloss and it's reasonable to assume that using D800s doesn't give you warts. I can't prove any of these, but they're reasonable assumptions given the lack of evidence to the contrary. And I haven't read any evidence here; forgive me if I've missed it.

More assumption from flawed logic.

Flattery will get you everywhere.

Nice attempt below at digging yourself out of the hole you dug. Have I endeared myself enough now?

As Carl Sagan said... "The absence of evidence is not evidence of absence."

I agree, but that supports my point. There's lots of evidence that the D800 focuses well. There's little evidence that it doesn't. The fact that we don't have evidence that the D800 works every time (which would be impossible) isn't evidence of a problem. As you say: "The absence of evidence is not evidence of absence."

Consider this... what's been suggested by Primeshooter (as well as Ming Thein, Lloyd Chambers, and others) is that PDAF on the D800 is less accurate and consistent than the D700. As such, a single mis-focused D800 image scaled to 12MP reveals little about focus accuracy in the absence of a D700 comparator image taken under similar scientifically controlled conditions. And given that the AF consistency of the D800 is suspect, really what's required here is a repeated set of comparison images scaled to 12MP.

Well, some VSPs (Very Serious People) say they've got a kind of feeling it's suspect without any definite evidence. As you say, that's not the result of scientifically controlled tests. And to say "...given that the AF consistency of the D800 is suspect..." to use your argument that looks like "an assumption from flawed logic".

Since this involves a lot of work and time (not to mention access to both a D800 and D700) it's somewhat unreasonable to ask a DPR member to report more than the empirical evidence of their relative experience of PDAF between the two cameras. My own experience is that the D800 is fine high resolution camera suitable for studio and landscape work when restricted to being mounted on a tripod and focused with Live View CDAF. For all other applications (reportage, wedding, sports, low light, and general use) the D700 is simply a better camera IMHO.

If I understand your argument: "Clever people have suggested that there's a problem but haven't done scientific tests, and it's unreasonable to ask them to do a lot of work to prove it, so we have to assume there's a problem." Hmm... I'm not totally convinced by that argument, if you don't mind my saying.

I'm afraid we do need more than empirical evidence to justify regarding the D800 AF as suspect.

Unless, of course, we're going to regard every camera as suspect because someone somewhere has said it doesn't work properly.

My, Simon, you're very presumptive to conclude all of this reverse hyperbole from my simple argument above. Basically the only thing I said was that your original conclusion about the absence of evidence being evidence of the absence of a problem was incorrect. That's just as true now as before you responded so it's not really clear you've advanced the discussion.

My only other point to the thread at large (and specifically to counter the attempt of certain D800 fan boys to squelch public discussion simply for lack of example images) is that empirical evidence should be the only threshold to posting in a users forum. It is after all a users forum, not a peer-reviewed publication where a higher threshold would be reasonable. It'd be pretty dead in here if everyone had to present scientifically valid comparative testing before commenting on their experience.


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