D800 Autofocus issues II

Started Jan 25, 2014 | Discussions thread
Simon Garrett Veteran Member • Posts: 6,047
Re: The absence of evidence is not evidence of absence

fPrime wrote:


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.

Apart from your comments about my presumption and your entertaining comments about digging, I perhaps agree with that, but I draw a different conclusion while using apparently the same logic.  (It was a misunderstanding to say that I was using the absence of evidence as evidence of absence, but perhaps what I said was open to misunderstanding.)

Anyone can post what they like (almost) here, and it doesn't have to be based on evidence, emprical of other. But we're also debating (in this case) whether the evidence as we each see it (whether posted or not) justifies the conclusion that "the AF consistency of the D800 is suspect". The evidence of which I'm aware doesn't come close to leading to that conclusion.

We can't take it as proven that the D800 is fault-free, nor can we with any other product.

In forming a useful judgement about whether there is credible evidence that "the AF consistency of the D800 is suspect" as you put it, one needs to balance the weight and quality of evidence for and against such a conclusion.  And clearly we'll each make our own judgement about both weight and quality in such a case.

  • On the one hand, we have evidence that the D800 is widely used, highly spoken of, and no reviews I've read make critical comment about AF (I'm sure I haven't read them all, and perhaps I've missed some such comment). I have read extensive reviews making favourable comparisons of the D800 AF with that of the D700. Examples of such favourable AF comparison I can find at this moment include Thom Hogan's guide to the D800 and the review on his site (both written well after the camera was launched, and after time for negative comments to come to light). Also the dpreview D800 review comments that the AF is slower than the D4, but otherwise makes only positive comments compared to other cameras. These are in-depth, technical reviews.
  • On the other hand, there are some comments you cite suggesting a problem. I don't place much weight on Amazon and other reivew comments. For every product there are always seriously negative comments, and the quality of criticism is often very poor. The same is true of positive comments on such reviews. I've not read comments from the photographers that you cite, but as you yourself say, they are not scientific assessments, unlike the Thom Hogan and dpreview reviews which include much more rigorous testing.

Now, which set of evidence looks more convincing to you? No need to ask, I guess, as I'm pretty sure we'll come to different conclusions!

None of this proves that there is no problem with the D800 AF, but I don't really think the evidence you cite, set against so many positive (and much more scientificly rigrorous) reviews and comments comes close to justifying the conclusion that "the AF consistency of the D800 is suspect". Just because some people criticise something doesn't justify an objective and balanced conclusion that it's suspect. This is the sort of lazy judgement hurried journalists are prone to make when they give equal weight to both sides of any argument, however preposterous. (I mean lazy judgements of journalists - not yours!)  A balanced judgement doesn't mean giving equal weight to all evidence.

I wouldn't for a moment try to censor primeshooter and others finding fault with the D800, but I think the debate needs a sense of proportion.

I'm not a "D800 fan boy [who wants] to squelch public discussion simply for lack of example images". But if people can't produce example images or other reproducable evidence, then the case for concluding that "the AF consistency of the D800 is suspect" looks a bit thin to me.

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