Single-point AF issue on D800

I'm a relative newbie, pushing myself with a series of semi-formal street portraits using available light. Handheld on a Nikon D800 with 28mm and 85mm primes, and a 28-300 zoom. Auto ISO in A-mode. I would frame up the shot, move the focus point to the face, half-press to focus, and then use continuous fire for 8-10 exposures before directing the subject, reframing, and selecting a new focus point. In almost all cases the face is out of focus.

I used the 'show focus point' plug-in to show me the focus point when the camera fired, and even if I have a face fully inside the selected focus point, the focus is somewhere else. In these two examples, the background is more in focus. Sometimes in a medium framing, selecting the eyes - the eyes are out but the ears are in, or the clothing on the chest is in.

Is the camera autofocus system failing, or have I made some errors? I've never seen these issues with this camera/lens combination before. As I was shooting I was trying different settings - switching between AF-S and AF-C to see if it helped get focus, trying to keep a shutter speed of 1/200 or faster.

Any thoughts on why this is happening?

The D800/e has known focus issues due to a possible crack in the chassis which causes focusing stability issues.

Here's a thread that includes pictures of the broken area - https://www.fredmiranda.com/forum/topic/1342802/0

With only two images for reference and much more extensive testing needed, suffice to say, there are several potential causes. Have a read about a manufacturing QA issue here:
https://www.dslrbodies.com/cameras/camera-articles/image-quality/d800-autofocus-problem.html

A cracked frame is another possibility. A warped or damaged lens mount flange could be another. A misaligned AF array could be yet another. Finally, it could be a combination of any or all of the above.

I'm assuming you bought the camera used. The best options are, if the camera has any warranty (e.g. bought used from a dealer with a 90 day warranty), exercise that option or just plain return it for a refund if within the return window.

If those are not options, look for an independent repair shop in your area.

If those aren't options, don't use the AF points that don't focus accurately. If your camera/ lens combo focuses accurately with, for example, the center AF point, AF Fine Tune will not help solve a focus problem with peripheral AF points.

Some D800 had a problem of accuracy of the outer AF points.

Truth be told, the central ones aren't the most reliable in the world, either.

This, of course, if you havent got a cracked frame (another known possible D800 issue), which unfortunately cannot be repaired.

Some D800/ D800e s just had screwy AF. There were (are?) fellows on here that sent them back to Nikon 2 or 3 times without any resolve. D810 cures that.

SteveJess said:

I'm a relative newbie, pushing myself with a series of semi-formal street portraits using available light. Handheld on a Nikon D800 with 28mm and 85mm primes, and a 28-300 zoom. Auto ISO in A-mode. I would frame up the shot, move the focus point to the face, half-press to focus, and then use continuous fire for 8-10 exposures before directing the subject, reframing, and selecting a new focus point. In almost all cases the face is out of focus.

I used the 'show focus point' plug-in to show me the focus point when the camera fired, and even if I have a face fully inside the selected focus point, the focus is somewhere else. In these two examples, the background is more in focus. Sometimes in a medium framing, selecting the eyes - the eyes are out but the ears are in, or the clothing on the chest is in.

Is the camera autofocus system failing, or have I made some errors? I've never seen these issues with this camera/lens combination before. As I was shooting I was trying different settings - switching between AF-S and AF-C to see if it helped get focus, trying to keep a shutter speed of 1/200 or faster.

Any thoughts on why this is happening?

Click to expand...

If you shoot afs the camera locks focus before you shoot, the slightest movement of yourself or the subject will render a out of focus shot. In AFC try one of the dynamic modes to see if you get better results, you could also try switching between focus priority and release priority. It is rare to get a oof shot using release priority.

--
Mike.
"I say we take off and nuke the entire site from orbit, it's the only way to be sure."

My D800 AF sucked, even after sending it to Nikon 2 times to have it adjusted. It was unreliable at best. The D810 was a so much better camera.

Seeing, that you are shooting wide open at f 1.8: Did you ever try Auto Focus Fine Tuning?

If not, try that first.

Markus

T O Shooter said:

Some D800/ D800e s just had screwy AF. There were (are?) fellows on here that sent them back to Nikon 2 or 3 times without any resolve. D810 cures that.

Click to expand...

This is true. Someone will come along and take issue though with their head buried in the sand.

The red boxes on the photo can be misleading: although the red box indicates which focus point had locked focus when the picture was taken, the focus point may not necessarily have been positioned on the face when the focus was locked.

For example, if you lock focus when the focus point is on the background, then recompose (without refocusing) such that the focus point is positioned on the face, it will appear as though the red box is located on the face, when in fact it wasn't when the focus was actually locked.

Not saying this is what you did, but the point is that there are inherent limitations with what the red boxes show.

btw, I have both a D800 and D850 which both focus perfectly fine for this type of situation.

My D800 was re-aligned by Nikon for the "left focus" issue, but this issue would not have affected this sort of situation. The "left focus" issue was something that only affected the extreme left focus points under certain situations, you had to look very carefully for it, and it altered the focus distance only very slightly (not greatly, like background vs subject in these photos).

I suggest try some other focus modes, like 3D tracking and continuous focus, although single AF should work no problem if used correctly.

One thing I notice is those backgrounds are pretty contrasty, almost like perfect focus targets. It may just be a challenging condition, where the background is easier to lock on than the subject.