D800 focus with 1.4 prime lenses is very variable and inaccurate

Started Jan 20, 2013 | Discussions thread
Jim Keye Senior Member • Posts: 1,947
Re: this is an interesting thread

primeshooter wrote:

Jim Keye wrote:

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.

Generally, but no afraid not. with 1.4 lenses the focus screen will not show your dof making it impossible to focus without the rangefinder dots.

Right, but there's still the option of following the focus shift as it goes back and forth, f2.8 or otherwise. But to be honest I haven't bothered to manual focus a hand-held lens in years. I just find the AF too good to bother with.

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.

I have worse examples.

Right. And that other fellow posted some examples. But, my point being, those subtle ones could be a resolution issue (as in, they weren't visible before). But the ones he posted (and I'm sure you have some too) are clearly not a resolution 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.

AF-C is worse and more jittery. AF-S should be able to cope.

Did you ever use AF-On/AF-C with your previous bodies? Because I'd be curious to hear your opinion of it in comparison to the D800.

Can you understand that Liveview contrast AF that takes about 4 seconds to lock focus gets me sharp shots at 1.4. How do you explain that one? In the time it takes to lock focus the subject could have jogged out of the focal plane, yet 100% of the time I use LV to focus I get a more in focus shot than the PDAF...I think this confirms my issue....

Well...yes and no. CDAF will be more accurate often, so it doesn't necessarily confirm anything. It does dispute the notion that it's subject or photographer moving the plane.

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.

It's random. Low contrast like the snow photos. Faces. The D800 is terrible with faces and f/1.4 unless contrast is HUGE on the face area.

I know, but the kid's face in tungsten light--can you recreate a similar tone with a static subject? Borrow a mannequin head, stuff animal, etc.

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.

It's good to vent.

Ha! True dat.

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