40D AI Servo and All Focus Points? I hate it... so far

I'm used to using AI Servo and a single focus point, but I wanted to increase my keeper ratio for sports and fast moving subjects (like my dog and birds). After reading a lot about AI Servo, I tried to activate all my focus points hoping that the center focus would lock first and then track from there.

NOPE!

My dog's head keeps getting beat by the blades of grass closer to me in the frame, and tree branches still cut my birds out of focus. How do you guys work with your AI Servo? Sometimes I think I should spring for the 1DmkIII and be done with it.

Surely single point AF is always going to be better than all points activated?

That's what I thought, as well. But, reading about AI Servo I found many users keeping all points activated.

Pete-eos wrote in post #5643680
Surely single point AF is always going to be better than all points activated?

How so? If grass blades keep getting in between the subject and camera and the camera keeps focusing on that instead of the subject, how is using a single AF point going to help in that case?

To the OP, AFPS is only really useful if the subject is moving around in the frame and you are having a hard time keeping a single AF point on the subject. If you are having issues with closer objects getting in front of the subject and throwing off your focusing, then a 1D series camera might offer a better solution. You can control the AF tracking "sensitivity" on the 1D series to control how quickly or slowly the AF point switches off a target when another object pops in front of the subject.

drPheta wrote in post #5643687
That's what I thought, as well. But, reading about AI Servo I found many users keeping all points activated.

Yeah, like Daniella over at dpr. Go here for some posts about ai servo on the 40d and when you get to page 2 marvel at her snowy owl pics: http://forums.dpreview​.com …19&thread=27362​248&page=1

It's horses for courses: it makes sense to use all focus points on a flying bird against an essentially featureless backgrounds: but for situations like

where there's stuff all around for any focus point to latch onto, single focus point is the way to go.

Rule of thumb:
featureless background, all focus points OK;
busy background (or foreground, if the clutter is under a focus point), single focus point good.

Easy.

All points focus is only good or accurate if the subject moving around in a wide open area (bird in flight shots and etc). Bird on a branch??? Single point. Is faster and what you point to and it will focus. All points focus make no sense in a situation like that because a small bird would not stay out in the wide open. Also, they tend to dash in and out of branches. As soon as they are behind a leave or a branch, there is no point in keeping it in focus.

With the markIII or markII, you can adjust the time delay before the AF system decides to switch the focusing point. Still, you can't get the shot because the bird is already hiding behind a leave or other branches.

drPheta wrote in post #5643661
I'm used to using AI Servo and a single focus point, but I wanted to increase my keeper ratio for sports and fast moving subjects (like my dog and birds). After reading a lot about AI Servo, I tried to activate all my focus points hoping that the center focus would lock first and then track from there.

NOPE!

My dog's head keeps getting beat by the blades of grass closer to me in the frame, and tree branches still cut my birds out of focus. How do you guys work with your AI Servo? Sometimes I think I should spring for the 1DmkIII and be done with it.

PacAce wrote in post #5643752
How so? If grass blades keep getting in between the subject and camera and the camera keeps focusing on that instead of the subject, how is using a single AF point going to help in that case?

Single point allows you to focus somewhere the grass blades etc aren't, whereas with AFP, there's no control over what might fall under a peripheral focal point, which the camera may well then lock onto.

I'll happily use AFP if I'm shooting BIFs against a clear sky or - if I was Daniella - against snow: but for pretty much any other situation, it's single point, and usually the centre unless I'm after a particular composition, in which case I'll enable a peripheral point.

Keith R wrote in post #5645979
Single point allows you to focus somewhere the grass blades etc aren't, whereas with AFP, there's no control over what might fall under a peripheral focal point, which the camera may well then lock onto.

I'll happily use AFP if I'm shooting BIFs against a clear sky or - if I was Daniella - against snow: but for pretty much any other situation, it's single point, and usually the centre unless I'm after a particular composition, in which case I'll enable a peripheral point.

In AIServo mode, AFPS doesn't randomly select it's AF points. The center AF point is used to acquire focus and it stays there unless the subject moves off of it. If a blade of grass gets in the way, focusing will shift to it whether you are using AFPS or a single AF point.

PacAce wrote in post #5646246
In AIServo mode, AFPS doesn't randomly select it's AF points. The center AF point is used to acquire focus and it stays there unless the subject moves off of it. If a blade of grass gets in the way, focusing will shift to it whether you are using AFPS or a single AF point.

Yep, but you're assuming that the photographer knows to acquire with the centre AF point. In my (specific) experience of this very situation, they often don't.