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by evan-pak

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When shooting events or action photos, engaging people, I often find that frontal (or rear) perspective may be very expressive, but my problem is focusing when the subject moves towards the camera (or away from it). I rarely have even a single decent shot in a series.

If I use AF, then the lag between autofocusing and the shutter release is long enough for the subject to move out of focus. This is especially a problem when shooting wide open. Burst shooting doesn't help here, because the subject is by definition moving more and more out of focus.

I tried focusing manually anticipating the subject, but my eyes are far from perfect in focusing, I often focus at the wrong plane (and it's hard to focus manually when there is nothing at that point yet).

What techniques do you use to shoot such photos?

share|improve this question
What model of camera do you use, and which autofocus mode(s) have you tried? – Rowland Shaw May 9 '11 at 12:54
My condolences. Poor AF on moving subjects is probably the worst thing about my K10D, and I think the K20D is not a lot better. – coneslayer May 9 '11 at 13:55
Nor the newer Pentax models. Continuous autofocus is the weak spot of Pentax's AF system, and this particular case is the worst of it. – mattdm May 9 '11 at 14:22
I'd just like to note that I'd really appreaciate MF tips and tricks. – sastanin May 10 '11 at 16:07
@jetxee — If you post it as a new question I'll totally vote it up. :) – mattdm May 10 '11 at 16:12
up vote 13 down vote accepted

This is a classic use-case for continuous autofocus (AF-C). Nikon uses that term, Canon refers to this mode as AI-Servo.

This does not guarantee anything though, just improves your odds depending on:

  • Which camera you use: Advanced cameras have predictive-autofocus which calculate the speed at which a subject moves and keeps moving the focus in that direction. This is to be used in combination with burst mode.
  • Which lens you use: Brighter lenses can focus faster even if you shoot at a smaller aperture. Different lenses also focus at different speeds for plenty of other reasons.
  • The speed of your subject: Obviously!
  • The contrast of the subject: Contrast is required to focus and the more contrast the easier it is to focus, so the lens can focus faster.
  • Shooting aperture: A small aperture gives you more depth-of-field so focus can be less precise. Keep in mind if it is too small, the shutter-speed will cause the subject to blur.
  • The focus point: In almost all cameras the center focus-point is more sensitive and can focus faster and with less light.
share|improve this answer
Predictive autofocus sounds like a cool thing to have, but my camera doesn't seem to do it (well), or simply the focusing speed is not enough. In AF-C it tends to stick to some focus positions for too long, before it starts readjusting. So it feels like delayed focusing, rather than predictive. But I'll try to test predictiveness of AF-C though. Thank you. – sastanin May 9 '11 at 13:53
Now that you added your camera information. I can confirm that it is true. I used to have a K20D and I now have a K-7 and K-5 but neither can do it, which is why I also have a Canon 40D for sports photography. – Itai May 9 '11 at 14:12
It seems I'll have to improve my MF skills... – sastanin May 9 '11 at 14:34

Unless your SLR has predictive/"intelligent" continuous autofocus, you're going to have a hard time overcoming it unless you have good enough eyesight and are quick at manually focusing. Unfortunately for most people, that's not the case.

Canon's continuous predictive autofocus is called AI Servo.

Nikon's is simply called continuous auto focus.

share|improve this answer
Pentax calls theirs continuous mode, and says this about it: "When the shutter release button is pressed halfway to focus, the camera automatically tracks the subject if it is determined to be a moving object." That implies some degree of prediction — but the problem is, it doesn't do it very well. I'm a Pentax fan, but this is a weak spot. – mattdm May 9 '11 at 23:11

You need to switch your camera to Continuous Focus. Focus Priority (Assuming your camera has such). Currently, Nikon is the only company on the market which provides the best AF for tracking subjects.

But most of all it takes a lot of practice to feel how the AF behaves on your camera.

share|improve this answer
Have you considered writing answers that don't involve switching to Nikon gear? – coneslayer May 10 '11 at 20:48
@coneslayer — agreed that that's not very helpful, but it is true that Nikon's continuous AF is better at this. I don't know if they're really the only company, but I don't think this deserves the downvotes. – mattdm May 10 '11 at 21:04
@mattdm I think it's safe to say that Canon's AF is decent with moving subjects as well, given their popularity with sport shooters. If @Ben hadn't also recommended a Nikon camera in the noise thread, I would not have made the comment.… – coneslayer May 10 '11 at 21:07
Listen dudes, if I said something untrue, say it, but dont criticize me for stating the fact. Yes, Canon AF is very good, and probably even faster at acquiring focus in daylight, but Nikon is better at tracking the subject in focus, and acquiring focus at low light. I know this from personal experience. – Ben Bibikov May 11 '11 at 14:30
You are phrasing your personal preferences and observations as very strong statements of fact. If something is based on your experience or subjective observations, phrase it as such. For example, you could say that you found the Nikon Foobar 3000 to be superior to the Canon 93 Delta for tracking moving subjects. When your first two answers here involve making very strong claims in favor of a particular manufacturer, without providing evidence, you come across as a shill. – coneslayer May 11 '11 at 15:15

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