Accurate Auto Focus System

Dominantly · Apr 2, 2010

Today while I was out shooting at a local skate park, I was really trying to utilize the cameras tracking, but it was just not as accurate as I would have liked. I know the AF system is reinforced by Nikon's scene recognition system, but I think the Multi-Cam 1000 AF module might be slower or less accurate then I had originally thought.
An example of what I was doing, I was tracking a dude on a BMX and panning with him as he approached various obstacles, the closer he got, the faster the action (I was shooting in 3D tracking). Now, I allowed the camera to SEE him and tried to get it to lock on, but the focus points would usually go sporadic, picking various objects around him. He was filling approx 60-70% of the frame, and his "color" was vastly different from the backgrounds.
I then went into Dynamic mode and had a bit better luck, but nothing really stellar.
I also would liked to have had the ability to move up to 1/8000, but whatever.

I'm really looking for feedback from folks with the D700 and D300s on this one. Lets say you are in Dynamic mode and you place your focal point on a subjects face, will the camera then lock on, and stay on the subject even with movement? With that "51 Group Dynamic with 3D Focus Tracking", if you point at let's say a person riding a bike right past you, will it stay locked as you pan with it? Is it as accurate with the subject filling a smaller portion of the frame?

Sw1tchFX · Apr 2, 2010

I have to go, but when i come back i'll tell you how I get in focus shots 95% of the time when i'm shooting running and cycling events.

Dominantly · Apr 2, 2010

Thanks, I look forward to it!

Moe · Apr 2, 2010

I recently got a D700 and have been looking into this. When taking action photos of my dog, I haven't been too successful when he's moving fast towards me (maybe I'm asking too much). It may be that my 300mm lens is a little slow, but I found some links and changed some settings. I haven't gotten to try this out as it's raining here, but here's the best one I've found. I don't know if it'll help you or not.

photography musings: Nikon D700/D3/D300 Autofocus settings

I'm looking forward to Sw1tchFX's reply as well.

Sw1tchFX · Apr 3, 2010

Ok, it's 12:30 am and i got back.

This is what I do and get a 90-95% or so keeper rate, basically to the point where if something's not right, it's my fault not the cameras.

It's similar to what Moe posted up.

The D90 is going to be a little different, but this is what I do on my D700:

AF-C

Ch @ 5fps

go into custom settings and set a1 AF-C priority selection to Release + focus, this way, the camera will keep tracking while you're shooting. Release priority waits till perfect focus everytime, and slows down fps, shooting priority slows down tracking for fps. Release + focus is the middleground.

than, i set a3 Dynamic AF area to 21 points so if i screw up and my subject goes off my AF point for a split second, the camera will keep tracking it though the surrounding 21 points.

settings a4, Focus tracking with lock-on i always keep off, partly because of original D700 firmware being buggy with it, and I found that it slowed down tracking slightly. so i just keep it off.

setting a5, AF activation, is set to AF-ON. I do this because it offloads the af to a separate switch as opposed to the shutter half press. Why? Because with the AF-ON button, if I just hold it down, the camera will continuously focusing all the time, regardless. If you have the shutter half pressed for AF, the camera often has trouble re-tracking after a picture is taken. Why? I don't know, but AF-ON is generally more reliable.

I also try to keep the subject's numbers in one of the center AF points, good runners generally stay straight, so if the numbers are in focus, the faces are in focus.

On the D90, since you don't have an AF-ON button, just use the AEL/AFL button to do the same thing. other than that, the custom numbers might be different, but the settings are the same. I'd probably set the center point to wide.

AF-S lenses generally help, most of them are faster to focus if you don't have a D1/2/3 or F5, the closer the distances the tougher it will be for ANY focus system, if you have a focus limiter on the lens, use it, it helps and yeah, just go at it.

the 51 point 3D tracking is a total joke, it's marketing ammo. I've never gotten it to work, and i have yet to meet or even see anyone have confidence in it.

I'll often shoot in manual mode too, as it's more consistent exposure from shot to shot, but if it's not manual, it's aperture priority with sometimes +0.5 EV comp.

So yeah, i use this technique on anything that moves, works prettygood with strobe work too.

I use it at the airshow:

The running events:

and the cycling events too:

I hope that helps!

fast eddie · Apr 3, 2010

Thanks for the tips Sw1tchFX, Great shots too.

Dominantly · Apr 3, 2010

Wow, thanks for the info. I am going to give this a whirl tomorrow for sure!
I'll also post up an example of a photo I lost tracking in.

Your photos are awesome, especially the last one. Great clarity and creative exposure!