Suggestions for improving D4 autofocus

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fhammond
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p.1 #1 · Suggestions for improving D4 autofocus

I went to our local pool yesterday and ended up with a lot of sequences like this:

This image is copyrighted by the owner

(I've zoomed in on the first photo to show it's in focus. There's a higher resolution version here.)

The first few images are in focus but when the diver gets lower and the background is more complex, the camera is switching focus to the background. In this example, the focus point was on the woman in the pink shirt. I looked at the shoot in Nikon ViewNX2 and this pattern - the focus point being on the background - was pretty common. Out of 126 photos, 50 were out of focus; a pretty high rate.

I was using dynamic focusing mode, and limiting the number of focus points didn't appear to make much difference to whether the photo was in focus. The lens was the AF-S 50mm f/1.4 G.

Towards the end of the shoot, I switched to 3D focusing and that seemed to improve the situation, though it's hard to be certain since I only took a dozen photos in 3D mode.

Any suggestions on how to improve things?

Aug 15, 2012 at 02:16 PM

Steve Perry
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p.1 #2 · Suggestions for improving D4 autofocus

Hmm, maybe try setting your custom function a3 (focus tracking lock on) to a longer length. It looks like it's not "sticking" to the subject long enough.

Aug 15, 2012 at 03:21 PM

chip_master
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p.1 #3 · Suggestions for improving D4 autofocus

Shooting fast action is always a challenge and is very variable.

1) I'm not a big user of primes, but from I've heard the 501.4 isn't the fastest lense. I'd not be choosing that for anythign requireing fast focus

2) Looks like you are in good light, in those conditiosn I ALWAYS stop down as much as I can and still get the shutter speed to freeze action. When background is as busy as you have than using longer focal length can narrow the DOF and get more subject isolation.

3) Just picked up my D4 but and still experimenenting but it seems faster. My settings are always fewest focus points I can get away with
a) AF-C? You have that set or on AF-S
a) 9pt, 21, or if I must 51point continuous
b) Depending how good I'm tracking as the other suggested focus track locking to shorter times. I find that is something you have to experiment with depending on how you use the AF-ON and contrast between subject / background and your ability to keep things on target. Generally I have it set on normal and still get good results with people running at me as I use AF-ON to keep center point on the subject

I have read that 3D focus is vastly improved on D4, but my trial and error experiments on D3s ALWAYS yielded better results with AF-C, AF lock Off/Short/Normal, and 9Pt or 21PT

Aug 15, 2012 at 06:49 PM

dj dunzie
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p.1 #4 · Suggestions for improving D4 autofocus

Steve Perry wrote:
Hmm, maybe try setting your custom function a3 (focus tracking lock on) to a longer length. It looks like it's not "sticking" to the subject long enough.

That's my advice too. For sports shooting - where board ads or spectators or just plain busier BG's can steal the AF track if you stray off subject (while panning etc) - it's a huge boost to the keeper rate at times. I don't blame the camera in this instance, you are dealing with a contrasty and busy BG and unless you're dead accurate with the AF track and panning smoothly with the subject the quickness of the D4 AF will grab those things you don't want it to.

Setting the lock-on to LONG will help you as you continuously AF and track a subject.

Aug 15, 2012 at 07:00 PM

fhammond
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p.1 #5 · Suggestions for improving D4 autofocus

Thanks; I'll try that out. The background is pretty much the worst thing you could have: busy and contrasty, just like you point out.

I was shooting also with a EOS-1D X and Canon's 50mm f/1.4 and it seemed to do a better job, probably because I'd already done what you described on the D4. ("Case 2: Continue to track subjects, ignoring possible obstacles" on the EOS).

I'll also try using the 70-200mm. However, I would have thought that lens focusing speed wouldn't have mattered as much here: the focusing system of the camera should prevent the lens from having to do much work, I'd think. (That is, the subject distance isn't changing much.)

Aug 15, 2012 at 07:09 PM

Taoguy
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p.1 #6 · Suggestions for improving D4 autofocus

Worth a read from Rob Galbraith's review, site still up. He found the following,

All of the above assumes the use of lenses like the AF-S 24-70mm f/2.8G, AF-S 70-200mm f/2.8G VR II, AF-S 400mm f/2.8G VR II and AF-S 200-400mm f/4G VR. What these all have in common is a maximum aperture of f/2.8 or slower. I've struggled to achieve the same level of autofocus performance with Nikon's f/1.4 lenses, including the AF-S 24mm f/1.4G, AF-S 50mm f/1.4G and AF-S 85mm f/1.4G. Even when the working aperture is f/2.8 and therefore shallower depth of field is not a factor.

As of this writing, I've not sorted out why f/1.4 lenses seem to bring about poorer AF system performance with the D4, or if there is a magic combination of AF settings that might alleviate the problem. With this camera, like the D3S before it, I've sidestepped the matter entirely by focusing in Live View instead. This has been a manageable workaround, at least for static subjects, but it's not much of a long term solution.

Aug 15, 2012 at 10:31 PM

fhammond
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p.1 #7 · Suggestions for improving D4 autofocus

Ah! That's very interesting. Well, a rematch is definitely in order, I think. Thanks for the reference.

Aug 15, 2012 at 10:33 PM

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