focusing on moving subjects

[miro]

I was doing some test shots of the wedding preparation and was supprised to see how many images came out blurry. I was using available light, and sometimes fill-in flash. Exposure was in 1/60-1/90 range with aperture of (usually) f1/4. Autofocus was on 'one shot', and images don't look like it's motion blur, but rather 'out of focus'...

How other people photograph people in motion with large aperture lens? What camera settings do you use? Autofocus one shot or ai servo? Any insight on this is greatly appreciated.

Cheers,
-Miro

[adamsmith]

Are you depressing the shutter release halfway at first, then all the way a moment later?

If so, your problem is the combination of one-shot AF and the shallow depth of field you get with a wide aperature. When I shoot moving targets with a tele on either the D60 or my Elan, I use AI Servo focus mode. AI servo continually adjusts focus for as long as shutter release is held half way down. One-shot only picks focus when the shutter release is first depressed halfway, then it locks. With one-shot, if your subject moves between the time you depress halfway and the time you take the shot, it may be out of focus. The shallower your DOF, the more this is an issue.

Of course, having a fast focusing USM lens helps AI Servo mode to track fast subjects.

-Adam

[miro]

Yes, that's what I thought... But what do you do if you want to take portrait photo of the person with the face in the focus, but you want the whole body to show? In other words, using one shot AF you would focus on the face and recompose the picture. What is the equivalent of that using Servo AI? If you have very shallow depth of field, focus on the face and focus on the waist might not be the same. Waist might be in focus but face would not. Am I overcomplicating the things :) ?

Cheers,

-Miro

[adamsmith]

It would be helpful to know more about your situation to determine what's happening. What focal length lens are we talking about? Is it an IS lens? F.L. of the lens has a big effect on whether or not you can expect to hand-hold a 1/60 sec exposure. Or were you trying to use one-shot focus on a moving person, and then recompose the image without refocusing?

That brings me to answer for your last question, how to deal with the focus point selection on moving people. The quick answer is that you need to pre select the focus point closest to the part of the person you want in focus. If you're turning the camera on its side to do a torso shot, you can still use AI Servo, with the left focus point active and always trained on the thing you want in focus (person's head). With a moving subject, obviously you don't have the luxury of being able to one-shot their face and recompose--that technique is best saved for posed shots--by the time you recompose an action shot, the person may have moved their head and you get a blurry face.

-Adam

[miro]

I'm using Canon 50mm f1/4 II lens. This is an unedited example photo. 1/125 @ f1/4. One shot AF. I took 3 photos in a row and the all look out of focus.

http://www.miro-michele.com/IMG_3241.JPG

Cheers,
-Miro

[adamsmith]

Do you have focus selection point on automatic? it looks like the camera chose the left focus point, and it focused on the bottom of her dress because it's closest. On the D30, the focus point doesn't flash red like it does on the D60 or Elan 7 does it? I think I read that it doesn't. Seems to me that this would make it harder to notice at the time of the shot that the camera was picking the wrong focus point.

If you manually set the active focus point to the rightmost one, and you make sure that's right on her face, it should work. Shooting at f/1.4 there is no room for this kind of error, DOF is really shallow.

-Adam

[miro]

Actually, middle focus point was selected. I focused on the face, recomposed and fired 3-4 shots...

[adamsmith]

You can't do this radical a recompose with wide aperatures because when you recompose, you tilt the plane of focus as you tilt the camera. You really need to use that right focus point for this shot.

-Adam

[miro]

AH, that's what it is. Thanks a lot !!!!

Cheers,
-Miro