1D AF tracking question.

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I currently use a 30D, and I know it's recommended to "track" a moving subject for about a second before firing the shutter to allow the AI Servo mode time to assess the subject's movement and focus appropriately. The problem is, whilst shooting a marathon for example, that the constant stream of runners means that there often isn't time to track each one for 1 second before firing, resulting in missed or out of focus shots.

My question is, does the AF tracking on the 1D series go some way to eliminate this, or do they also need the same 1 second tracking period before shooting a moving subject?

Thanks.
 
The cameras can acquire focus very quickly these days, but it is helpful to leave it a second or so to allow it to actually lock to the subject (ie, judging its movement and ensuring it stays with it). It also gives you visual confirmation, especially at wider apertures where you're going to get a shallower depth of field!

With regards to the runners, I'd just shoot at a slightly narrower aperture and let the increased DoF take care of the rest, don't worry too much about where you're focussed as long as it's somewhere in the group! (Unless of course you just want one of the runners in particular, then your panning and tracking skills are going to need some polishing!)
 
There's no doubt that technology is amazing are we're spoilt these days.

To be honest, the AI servo mode on my 30D still amazes me, despite its age.

I suppose my question really is: am I asking too much, even of a 1D series, and should alter my approach instead?
 
The 1D series does go some way to addressing this, you can set the focus tracking sensitivity.

I'd suggest renting one for a few days to see how you get on with it, they do take a while to get dialled-in to but once you get your head around the controls you'll love it.
 
I think it's important to understand what's happening before deciding how much quicker the AF is on a 1D versus an xxD body.

AIservo is a multipart part operation and, for the purposes of illustration, can be summarised as;
1A...Calculation and command to the lens
1B...Lens focus move and confirmation
1C...Body checks focus
2A...Subject distance change calculation and command
2B...Lens focus move and confirmation.

Clearly the B events are lens dependant whilst the A's are body dependant.
1B can be a large part of the total 1A-1C time whilst 2B can be a very small part of the 2A-2B time assuming that the focus change isn't too great....an approaching runner will require less correction than an approaching racing car.

In a nutshell....
Use an EF85/1.2L and the time gained by switching from a 30D to a 1DIV will be a relatively small percentage of the total. The same scenario with an EF135/2L will give a much higher percentage improvement by changing bodies.

Bob
 
Thanks for the replies folks, and the breakdown Bob, plenty to think about.

I was using a Sigma 70-200 2.8 EX II HSM DG Macro at about F/4, ~800th. I wasn't firing continously between runners - I'd fire a 2-3 frame burst at each as they approached, let go of the shutter and back-button (using BBF) whilst panning to frame the next runner (using a monopod), tracking for perhaps 1/3 sec with the back-button before firing another 2-3 shot burst, rinse & repeat (unless there was a gap, in which case I'd pan the last runner much closer, zooming out as he approached).

My gut feeling was that the lens was keeping up fine, but perhaps the 30D wasn't able to do its processing quickly enough.
 
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1D is incredibly good at quickly locking and tracking focus. I had taken sharp shots at f/1.8 when I didn't even expect it to nail it.

But my other concern is, that surely if you shoot every race participant 2-3 times, you will quickly burn out even a 1D body... Race winner and a few top places and your mates would be a fair deal, but sounds excessive to me.
 
I say every runner, in reality very often there were tight groups of 3,4 or 5 runners which I'd capture together, but it was a narrow section of track (cross country) and the going was pretty hectic!

By the sounds of it, a 1D series should improve things. I'll take up the advice and try one out for while before deciding for sure.

Edit: I try and shoot as many runners as I can for two reasons: a manic obsession to practice :) and to capture some interesting shots. This chap for example. I also have shots of people running in pain whilst frothing at the mouth but I'll refrain from posting those. :)

 
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