Auto focus whilst panning

Hi all
Hope I have posted in the correct place as this is only my second post.
Can some one help me, whilst panning is it better to use just the center auto focus point or have all the points turned on.
Cannon EOS 400D, Sigma 120-400mm lens.
My main interest is aircraft and wildlife.
Thanks
Jeff.

fiestyfox wrote in post #10338671
Hi all
Hope I have posted in the correct place as this is only my second post.
Can some one help me, whilst panning is it better to use just the center auto focus point or have all the points turned on.
Cannon EOS 400D, Sigma 120-400mm lens.
My main interest is aircraft and wildlife.
Thanks
Jeff.

I tried one shot and found it too hard to keep the one point on subject while it is moving- and if it is quite small in frame.
Are you using AI servo & AI focus. (I assume 400D has both)

Aircraft or birds in flight I'd use all points-there's not much the camera can focus on except the subject. On the ground center point would probably work better because of foreground and background clutter.

For the 400D, I'd use just the center focus point. More advanced cameras have very strong off-center points, but even then the center points are the most reliable and well-developed. And, when you are panning with AI Servo, to me it's important to keep the center tracking as accurately as possible -- if you let a subject drift off to the side you might lose it altogether.

But, that's jut me. I dont' know how well-developed AI Servo is in the 400D, but if it is in fact "functional" with all points enabled, it wouldn't hurt you to play with it. Just try not to try it on critical shoots unless/until you really know how reliable it will be.

I can tell you I've tried using other points for rally shots and the results were unreliable at best. My keep rate was much higher when using the centre point.

While you are panning (shutter is open, image recorded, viewfinder black) the camera will not change focus, so it doesn't matter how you focus. But I assume you are tracking the subject and taking multiple shots, panning each of them. In that case it may be beneficiary to update the focus setting between shots.

To do that you have to have Servo AF selected. If you use One shot AF, the camera will focus only once, and then keep the same distance setting as long as you keep the shutter button half pressed.
When using Servo AF, you have to either select one single AF point and maintain that on the target, or use all nine points at the same time. If you go for the second alternative, note that you always have to start acquiring focus with the center point. But if you do loose contact with the subject with the center point, and the camera then can determine that one of the other points still is in focus, it will hand over focus tracking to that point. If no other point is in focus within a certain time interval (which cannot be set on a camera like the 400D, but will remain fixed at about 0.5 seconds), the camera will attempt to re-acquire focus with the center point.

When you are tracking with multiple points, the camera may very well find something else than what you intended to focus on. In such cases, using one point is better, but it will require that you keep that point on the target.
Thisis a typical case, where the camera wanted to focus on the high-contrast commercial signs in the background, instead of on the runners.
In such cases, I recommend that you remove focus from the trigger button, but instead focus with your thumb. On the 400D, this means using the * button for focus. By doing like that, you can temporarily stop focusing, if you realize that for a certain time, the camera may just be confused, so it's better to just keep the current focus setting, or focus manually if your lens allows that. Takes some practice, but works better once you've learned it.
It also helps in situations like this one, where there are trees both in front of and behind the runner. Being able to control when to have servo focus active or not helps in such cases, especially with cameras lacking the more advanced modifications to the servo AF algorithms that are possible only with the 7D and other cameras in the 1D series.

oldvultureface wrote in post #10338804
Aircraft or birds in flight I'd use all points-there's not much the camera can focus on except the subject. On the ground center point would probably work better because of foreground and background clutter.

agree completely. I'll add to the pile that mention the fact that AI servo is the way to go as well.

As a general rule, it's perfect. But all generalisations are dangerous - this one included.

Here's the first imagein a series, where the camera's multiple AF point system (center zone AF on a 7D) is used to make it possible to put at least one AF point on the target, in spite of several obstructions between the photographer and the subject now and then. It doesn't work all the time, but still surprisingly well. Admittedly, the 7D's AF computation capability is a bit more powerful than most other camera's.

This series isn't relevant for aircraft shots, but could very well be for wildlife.

Hi all
Thank you all for posting replys to my query.
I will take on board the info and advice given and get out and about next weekend and practice my panning.
I am wondering if the 400 body is not up to the job with the larger heavier lenses and its time to upgrade.
I have had good results with lenses up to 200mm but focus is generally on the soft side with the 400mm lens.
Will post some results.
Thanks again,
Jeff.

The focal length shouldn't matter - the 400D is perfectly capable of being used with long lenses. The only weakness in the focusing that I've found is with very fast lenses (f/2 or better), where my 40D is a little better.

If you go to my motorsports galleries HERE, the two Sunseeker Rally galleries, and all the Goodwood ones up to and including "Goodwood Track Day 23/08/08", were shot with a 400D. A large proportion were shot at 420mm (300mm f/4 L with teleconverter).

apersson850 wrote in post #10339883
Here's the first imagein a series ...

Amanda has lost all credibility as a fashion conscious and sane young woman. Hope no one else was watching.

Hi
Heres some pics, tried some differet settings and techniques, having trouble holding the camara steady.

It looks like you done pretty good! Next time around, for the prop planes, try working at a slower shutter speed to get a little more blur! This is fun stuff to play with!

Nice! If those shots were mine I'd be happy.

Centre point and AI Servo works for me..

Here are some more http://www.pbase.com/j​urgentreue/bears&page=​all

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