D800 focus with 1.4 prime lenses is very variable and inaccurate

Started Jan 20, 2013 | Discussions thread
Jim Keye Senior Member • Posts: 1,939
Re: this is an interesting thread

primeshooter wrote:

Please stop. Just stop. Also you seem to not understand how manual focus works so let me explain to you. The D800 focus screen sees f/2.8 dof only. This means that factory standard D800, you cannot manually focus the D800 with a 1.4 prime at 1.4 without using the rangefinder confirmation dot (nothing will change in the viewfinder when you open up from 2.8-2-1.4. And therein lies the issue. If you pull focus to that dot and your getting front and back focus with autofocus on your camera - you are more than likely going to get it with manual as the lens "thinks" this is correct focus when the dot shows.

Hmmm. I always thought the point of manual focus was to use your eyes. That's why I switch to it--the whole point is not relying on the camera.

But that aside, what are the options here?

  • There's an actual problem with the D800s.
  • There's a problem with your/some D800s.
  • There's a problem with your technique, and/or your technique in conjunction with the D800 AF
  • This problem has always been there, it just wasn't as obvious until you magnified 3x with a D800.

In some cases you've stated the focus is so far out that it's not a MP issue, but your kid/snow photo isn't that far out at all, and seems like it could be potentially hidden by the the lack of resolution.

The nose photo is interesting because the nose is so clearly in focus, especially contrasted against the dark hair, that it appears as if the camera chose to go there rather than front-focusing. But I guess it could just be coincidental.

What we do seem to hear is that some people have this problem, and some don't. Some are in fact quite happy with their D800 AF. This suggests either a quality control issue or a technique issue.

I know you're swearing that this is unique to the D800 and not you, but of course on a forum it impossible to tell. Please don't take that personally. I have to say, AF-C and the AF-On button are the ONLY way to go. The fact that you're having more problems with that set-up than AF-S has me questing technique.

But, have you borrowed another body to see if it does the same thing? Could you have someone else stand next to you and shoot the same thing right after you and see if they have the same problem? Have you mapped the size and location of the AF sensors? Is the problem better or worse on a tripod? Is the problem related to the color of light, or just the light level? Is the problem something you can recreate?

Can you set up a scenario that triggers the mis-focus?--as random as it might be, at least it does happen some of the time in this scenario.  That would be ideal because then you could start eliminating more variables.

But to be honest, I'm not sure there's anything on this forum that is going to help you. In part because not everyone has it--this suggestions QC--and in part because we can't be guaranteed that it isn't technique.

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