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Predictive Autofocus for birds in flight

Robert Melone , Mar 10, 2011; 11:53 a.m.

I understand that some cameras have a predictive autofocus feature, where the camera locks onto the subject and tracks its movement across the viewfinder, allowing for better handheld shots of birds in flight. Is this 3D-tracking in Nikon cameras, have you used it, and how does it work? What other techniques do you suggest for capturing quality images of birds in flight. I am using a D90. Thanks.

Responses

Kevin Chow , Mar 10, 2011; 12:32 p.m.

Yep, this is the 3D tracking AF mode. In the D7000 (and probably by extension, to the D300 as well), you stick part of the bird in the selected focus point (which you can move about as you would normally), half-depress the shutter release to the focus detent and then hold it down while tracking. It uses some image pattern recognition algorithms to try and keep whatever you focussed on as the focus point, so as the bird or object wanders around the frame, the AF point tries to follow it.
It works fine against a clear sky, but if you're shooting against very contrasty backgrounds, it can get lost.
I use a combination of 3D tracking and 9-point AF when shooting birds. 3D tracking on the '7000 works pretty quickly, and unless you're using a fast lens that can keep up, it can hunt. It works fine with my 70-300 VR, but the AF in my Sigma 150-500 is too leisurely, so it doesn't work so well - in that case I just use single or 9-point AF. In recent experience shooting waterfowl with the sigmonster, I stuck mostly to 9-point AF - partly because of its AF speed, but mostly because most of the time, birds were far away enough to give me time to pan around and take my time.

Rick Sands , Mar 10, 2011; 12:33 p.m.

Have a look at AF-C, and use 3D-tracking under custom setting A1.
Thom Hogan's book does a really good job of explaining this. I have a D90, and use this (along with a Nikkor 70-300) to track birds in flight; works well.

Frank Skomial , Mar 10, 2011; 02:16 p.m.

3D tracking auto focus uses focus distance information, usually provided by current line of Nikkor lenses.

Some 3rd party lenses do not provide the focus distance "D" information, and Nikon DSLR must give up use of this crucial for 3D tracking data, or use a less accurate tracking algorithm, sometimes just substituting focal lens length instead of needed precise focus distance data.

Even if some 3rd party lenses have built-in CPU, one should not assume that the lens also provides focus distance information, that is too comon mistake and assumption on some lens advertising sites. To provide usable for 3d focus tracking precise focus distance information, additional in-lens electronics, and data processing is needed. Something that is missing e.g. from Zeiss, and other fereign makers lenses, that possibly have a CPU built-in..

Elliot Bernstein , Mar 10, 2011; 02:22 p.m.

Predictive AF and 3D tracking are different from each other. I believe it is a feature built into mostl Nikon DSLR cameras when shooting in AF-C mode. Shooting birds in flight, unless they are larger, is difficult even with Nikon's best DSLR bodies. 3D may work better (depending on the shooting conditions). There are a lot of variables that come into play with focusing when in comes to birds in flight.

Here is some information you may find interesting about predictive AF:

http://www.nikon.com/about/technology/core/software/caf/index.htm

http://www.nikonians.org/nikon/d200_multi-cam_af/nikon_d200_multi-cam1000_review_3.html

Jay Poel , Mar 10, 2011; 03:52 p.m.

I have a D90 and it's pretty cool to see it in action in the viewfinder - the autofocus points will light up around the viewfinder as it tracks the initial target (or move your camera side to side and the active focus point will switch to stay on target if the object is stationary and you want to see it working).
As Kevin said, it works better in high contrast scenes (dark bird on a blue sky, etc).

William Pahnelas , Mar 10, 2011; 05:49 p.m.

maybe the next generation of nikon bodies will have a useful implementation of the 51-point 3D tracking AF, but this go-round, it doesn't seem quite ready for prime time. give the AF module no more info than necessary to track your subject, and it'll lock on and keep tracking more reliably.

Juan Parmenides , Mar 11, 2011; 01:41 a.m.

For marine birds (and as well for common birds too) I use AF-C with 3D with very good results, 99% of the pictures are sharp focus.

Elliot Bernstein , Mar 11, 2011; 06:08 a.m.

William,the D7000 is the next generation and it does work well with it, as it does with the D3/D3S bodies.

Robert K , Mar 12, 2011; 07:54 a.m.

You may find the references in my post here helpful:

http://photo.net/nikon-camera-forum/00YN7r

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