Nikon D800 Autofocus setting

I have a Nikon D800 and have been mostly using it to shoot my 18 months old kid indoor. My kid is moving a lot so I have been trying to experiment with different autofocusing settings. But I think I need some help as I don't think my AF-C setting is right. When using AFC-Auto or AFC-3D, I can see the focus point move along with my kid. But when I use AFC-51, 21, 9, when my kid moves, the focus point never move. I don't think this is normal, is it? My understanding by reading the manual is that in the 9, 21 or 51 point mode, upon locking the focus, the focus should move when the subject moves.

The reaon I want to try 9, 21 or 51 is due to the fact that when I use fast prime, such as 85 f/1.4, 3D tend to lock onto my kid's shirt instead of the eyes. AFC-Auto is not always reliable either. My ideal AFC mode will be to first use the select focus point to lock to my kid's eyes, then track the eye by using one of the 9,21 or 51 focus point. Everything I read, 9 and 21 are more reliable than 51 point. Any help?

glcheng said:

glcheng wrote:

But when I use AFC-51, 21, 9, when my kid moves, the focus point never move. I don't think this is normal, is it? My understanding by reading the manual is that in the 9, 21 or 51 point mode, upon locking the focus, the focus should move when the subject moves.

Click to expand...

It is normal. With dynamic area AF-C (with 9, 21, or 51 points), the focus point does not change. As the manual says, the surrounding points assist if the subject briefly leaves the selected point. But that's all.

The focus point does change with 9, 21 or 51 point, but it does not show that change in the viewfinder.

9 and, to a lesser degree, 21 point will react quicker and often be more consistent than 51 point as those modes cover less of the viewfinder area, meaning there is less surrounding data to process and consequently less data for the camera to get confused by. But as those modes cover less of the viewfinder area they are also more likely to lose the subject if it strays wildly from your originally chosen focus point.

3d af will track colours very well, but can become confused by other surrounding similar colours or tones. Auto af with face detection should track faces well, but can be confused if the subject turns sideways or shuts one eye for example. It will also take the decision of which face it tracks out of your control.

For moving kids I think the D800 af is not sophisticated enough to hold focus on a small element like an eye. The best you will get with any consistency is focus on some part of the face. If the background is relatively disimilar in colour to the face then 3d af is probably the way to go. If the background is more similar in colour then 9, 21 or 51 point may be better, but you will not see what it is focussing on until you review the image.

Personally I find auto af with face detection too tempremental for moving people and using it takes too much control away from the photographer.

I hope this helps?

glcheng said:

glcheng wrote:

I have a Nikon D800 and have been mostly using it to shoot my 18 months old kid indoor. My kid is moving a lot so I have been trying to experiment with different autofocusing settings. But I think I need some help as I don't think my AF-C setting is right. When using AFC-Auto or AFC-3D, I can see the focus point move along with my kid. But when I use AFC-51, 21, 9, when my kid moves, the focus point never move. I don't think this is normal, is it?

Click to expand...

That is normal. Even though you don't see the active focus point moving, they do assist in focus tracking. The problem is that unlike 3d tracking, you would have no way to know whether those supporting focus points really were on your subject or tried to nail a background object.

glcheng said:

My understanding by reading the manual is that in the 9, 21 or 51 point mode, upon locking the focus, the focus should move when the subject moves.

Click to expand...

That is an incorrect assumption if you mean the active focus point change would be displayed in the viewfinder.

glcheng said:

The reaon I want to try 9, 21 or 51 is due to the fact that when I use fast prime, such as 85 f/1.4, 3D tend to lock onto my kid's shirt instead of the eyes. AFC-Auto is not always reliable either.

Click to expand...

In general, I have not been very happy with AF-C performance of my D800 compared to D3, which appears to nail focus at a much-much higher success rate. Out of all, AF-C Auto has been the most successful. But I won't say it turns out to give a high keeper rate. It does not bother me much because I don't typically use the D800 for tracking fast moving subjects. My D3 does that to my total satisfaction. I use D800 to shoot stationary objects - mainly landscapes, cityscapes, nightscapes, where it beats the craps out of D3.

You might try a couple of experiments - it's not like your subject matter will be difficult to motivate....

First, try to get the focus point where you want it. Unlike some of the other posters, I've found that Nikon's AF whatever-the-new-gizmo-setting-is doesn't work as well as I wanted it to. I've always gone back to single point when I really want to have the picture focus set on a specific feature - like the eye of a bird. You do have to plan ahead and be able to compose the shot in your mind. Again, with your kid busily running about terrorizing the room, it's not like you won't have lots of opportunities.


If, however, you're trying to get the entire child in focus, (say you want a picture at a party or some other hard to replicate scene and you are acting more as a photojournalist than an artiste), then you use the hand grenade approach. Use whatever focus setting gets you most of the way there, then adjust your depth of field as appropriate. With a D800 and assuming you don't plan on printing the picture as as wall sized poster (Childzilla?) nor crop at 100%, then you can go up to 3200 -6400 pretty easily. This gives you unparalleled freedom as far as DOF. Thus, having the camera hone in on the shirt is fine as the head and rest of the body will be pretty much in focus around f/8 or so.

Couldn't do that in the past without additional light but the high ISO capability of the new Nikon cameras is just amazing.

I use AF-C and 9 points all the time on fast-moving subjects. I also set AF lock on to the lowest setting so that the camera can react quickly to fast changes in both the subject and to focus on new subjects if I decide to shift targets.

Thanks for all the comments and suggestions, folks. I was mostly frustrated when using large aperture such as f2.0 and shooting fairly close (5-6 feets) as I typically want to get a fairly tight shot. Look like I do need to play with 9 and 21 focus point and see the picture and see if they impeove my success rate. With kid, my initial impression is that AFC-auto is more consistent than AFC-3D, which tends to lock onto my kid's shirt way too often (I guess he tend to wear bright color short).

The other thing that I realize is that fast zoom like 70-200 mm f/2.8 does better than fast prime such as 85 mm f/1.4 G. The focus lock faster with the zoom, and with VR I can get away with shutter speed 1/100 and really good success rate. I was hoping to use the f/1.4 of the prime to hold ISO down (I still don't liek to go above 3200 with D800), but realizing that the depth of field at close distance is just too thin and my D800 is still not focusing fast enough.

Try setting custom setting A3=OFF. Give it a try, then try same with 1 (Short).

mibadt said:

mibadt wrote:

Try setting custom setting A3=OFF. Give it a try, then try same with 1 (Short).

Click to expand...

To the OP, do this, it will help make a difference. The other advice you got so far is also right on the money. Unless my target (well defined/contrast) is moving around rapidly, I use AF-C single point, the D800's focus speed isn't as fast as my D3s or D3x but it seems very close!

glo