D90 autofocus and moving subjects

[michael_b6]

<p>I've been playing around with a new D90, trying to figure out the best A/F settings for focusing on moving subjects like kids or animals. I'd really appreciate any tips on what settings work well for this, as well as any techniques that contribute to success. I've been switching between AF-C + dynamic area and AF-C + 3D tracking, and so far I'm not super impressed with the results I've gotten. Frankly, the 3-D tracking seems basically useless to me. If anyone does use this and finds it helpful, I'd love to hear under what circumstances. I thought 3-D would allow me to focus on a subject (especially with shallow depth of field), and have that subject remain in focus even if it moves between the time I acquire focus and release the shutter. Perhaps I misunderstood? And, as an aside, how much better is the D300 than the D90 at this kind of thing?</p>

[Matt Laur]

<p>The better the light, the faster the lens, and the more contrasty the moving subject, the better it will work. This is true of both the D90 and the D300. The D300 has more focus sensors, and more of the "better" (cross-type) ones that work on trickier subjects. It's not magic, of course. But I can tell you that the D300 is substantially better at that situation than is the D200. The D300 has a more granular focus system than the D90, and it's a real part of why it's a more expensive camera body. <br /><br />What lens are you using, and under what sort of lighting conditions?</p>

[rarmstrong]

<p>Michael, don't despair, with more experimentation you will find the situation where it works best for you. The D90 has Nikon's multi-cam 1000 AF module with 11 focus points and only 1 cross type sensor. The D300 has 51 points with 15 cross type sensors and the more advanced multi-cam 3500DX module.<br>

So what....well, what it boils down to is that the sensors need contrast and enough light to differentiate your subject from the background and things around your primary focus point. The more cross type sensors, the better. With the D300 the 51 point dynamic system with 3D tracking works just great for a moving subject against a bland background(like a large bird against blue sky). But, if the bird flies below the tree line, the camera gets "confused" and it's better to return to a single focus point and follow the subject.<br>

In fast moving sports situations, I've found that using a single center point on the player of interest is best, because the camera really doesn't "know" what you want in focus in the middle of all that fast moving stuff.<br>

Try the 11 points with 3D tracking on something against a bland background with good light and see what you think. Even with a great 51-point system, I often find that the single point, kept directly on my moving target is the best.<br>

It works, it's just not magic.<br>

Have fun with it!<br>

Dick</p>

[michael_b6]

<p>Thanks for the answers. Richard, when you suggest using a single point, kept directly on the target, are you using AF-C/dynamic area? I suppose the lens I've been using could be partly responsible - the 50mm 1.4D (not the new one) - which isn't the fastest focusing lens out there. And, yes, the autofocus system was the one thing really nudging me toward the D300, but other factors swayed me to the D90. Besides this one thing, I've been really pleased with the speed and accuracy of the D90's af; even the non-cross-type sensors seem spot on, and much better than the D70.</p>

[rarmstrong]

<p>Try using it on AF-S at first so you can get the feedback of locking on the focus from the camera. On the D300 that will light up the central single sensor in the viewfinder and give you a beep(if you have it turned on). The sensor rectangle will light up red when the focus locks on, when you press the shutter button half way. Even my non-AF-S 80-400 zoom locks on quickly when it detects focus. I think it's the same on the D90. You should also set it to AF-S and try the 11-point with 3-D tracking as I mentioned above. Once you get used to it you might find you like to set it to AF-C for some situations. If you are interested in really digging into your camera, check out the guide available from Thom Hogan at bythom.com. You'll find it here...<br>

<a href="http://www.bythom.com/nikond90guide.htm">http://www.bythom.com/nikond90guide.htm</a><br>

<br />Dick</p>

[johannes_sigl_r]

<p> <br>

OK, now I'm confused. :-)</p>

<ol>

<li>AF-S + Single Point: User selects focus point manually using multi selector; camera focuses on subject in selected focus point only.<br /></li>

<li>AF-S + Dynamic Area: User selects focus point manually using multi selector; camera focuses on subject in selected focus point only.<br /></li>

<li>AF-S + 3D-Tracking: User selects focus point manually using multi selector; camera focuses on subject in selected focus point only.<br /></li>

<li>AF-C + Dynamic Area: User selects focus point manually using multi selector; camera will focus based on information from surrounding focus points if subject briefly leaves selected point. <br /></li>

<li>AF-C + 3D-Tracking: User selects focus point manually using multi selector; if user changes composition after focusing, camera uses 3D-tracking to select new focus point and keep focus locked on original subject while shutter-release button is pressed halfway.</li>

</ol>

<p>So should I use <b>AF-C + Dynamic Area </b>for subjects that may leave the manually selected focus point? And <b>AF-C + 3D-Tracking </b>if I might want to change the composition??<br>

Thanks/Jo<br>

 <br>

 </p>

[rarmstrong]

<p>Jo, the answer is really yes and yes:-), but, you really need to pick one of those settings in a situation that you think it will help or want to try, and try it out. Keep track of what you are doing and review the images on your computer. You will learn what you like the most about each option.<br>

Matt may have more to add about how he sets up his D300 for running dogs and outdoor hunting shots. Most of my experience so far is with large flying birds and some limited sports shots, outdoors in daylight.<br>

Dick</p>

[johannes_sigl_r]

<p>Richard, thanks for your reply! :-)</p><p><br>

But what does it mean if you say 'return to a single focus point and follow the subject'? Are you using AF-S together with Single Point? With Dynamic Area? </p><p><br>

Does the camera re-focus at all if I use AF-S for moving subjects? In the selected focus point? And regardless of whether I use Single Point, Dynamic Area, or 3D-Tracking?</p><p><br>

Thx/Jo<br>

 </p>

[rarmstrong]

<p>Jo, what I do when I'm following the subject is use AF-S with a single point and keep the point on the subject while intermittently pressing the shutter button halfway. The camera is relocking the focus each time. I'm used to this because it is the same way that I did it on my old Canon film SLRs. If you are speaking of the D300 you can also set it up to use the AF-ON button at the upper right of the back of the camera with your thumb, instead of pressing the shutter button half way. If you do that, you have to coordinate your thumb and index finger so that your index finger is just doing the shutter release.<br>

Dick</p>

[johannes_sigl_r]

<p>I see! YOU are the tracking system that keeps the focus locked on the original subject... ;-)</p>

<p>Jo</p>

[rarmstrong]

<p>Yes, here is a good example of using a single point with AF-C with a D300 at 8 fps...<br>

<a href="http://www.photo.net/photo/8712971">http://www.photo.net/photo/8712971</a><br>

The photograher who took the shot does excellent work with large birds.<br>

Dick</p>

[steve_king5]

<p>AF-S locks focus; I think what you want is AF-C.</p>

<p>Do a search a week or two back on auto-focus and the D300, and in the thread is an article on how to use the AF ON button. On the D90, you can set things up to do the same thing, by assigning the function of the AF/AE-Lock button.</p>

<p>It could not be easier -- static subject? Put the focus point on the subject, and tap the button once. Recompose if desired. Moving subject? Put the focus point on the subject, and keep the AF-On button held down while you're shooting. I've not found a more effective way to use AF and the D90.</p>

<p> </p>