40D with 2.8 - Focus - Action Shots

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Spaceman

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Hi - new here.

I have a 40D and use the 70-200 F4 L lens, mainly for action shots (working dogs).

Thinking about buying the 70-200 F2.8 L - mainly for the extra stop to keep the shutter speed up.

The high precision focusing at 2.8 - is it good for AI Servo and action shots - anyone used it?

Its a significant spend - trying to make sure its the rigth way to go:)

Thanks
 
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Got a nice poster printed for my wall, and that was with the IS off the focusing is lightning fast.
 
Not wanting to put anyones nose out here but that photo was taken at f10 so it hardly answers the original question. You could get similar performance with the 70-200 f4!

I suppose the perfect example would be say, a football match on a cloudy day?
 
Actually, if you understand how the AF works then you would know that its got nothing to do with the aperture value set for the actual photo itself.... the aperture opens all the way up for AF to take place....and also on the 40D with the centre focus point active only, this will also engage the precision AF mode when F2.8 or greater glass is fitted.

So, yes, it does make a difference and not just to allow you to take pictures in 1 stop less of light.
 
Sharp and full of color shame about the crop losing part of the front wheel. Great shot well done.
 
Spaceman said:
Hi - new here.

I have a 40D and use the 70-200 F4 L lens, mainly for action shots (working dogs).

Thinking about buying the 70-200 F2.8 L - mainly for the extra stop to keep the shutter speed up.

The high precision focusing at 2.8 - is it good for AI Servo and action shots - anyone used it?

Its a significant spend - trying to make sure its the rigth way to go:)

Thanks
Click to expand...

Hi, This shot was taken with my 40D and a borrowed 70-200 2.8 IS. I was using IA Servo and the centre focus point, the focus was pretty much instant and perfect at all times.
bustersheba-2.jpg
 
Sorry peeps, I wasn't thinking of the question regarding the focus speed, more the "mainly for the extra stop to keep the shutter speed up".

But I obviously agree with the above sorry for the confusion.
 
There was 2 questions there really, about keeping shutters up, not something i generally worry about more keeping them down lol

and about ai servo speed, the f2.8 is a tad faster and more accurate the 400mm f5.6 if you switch the focus limter on the 400mm to its lowest setting, but not much different with the limter increased, although primes are generally quicker then zooms anyway. once the 70-200mm gains lock it very really loses it, the 400mm can easily lose lock if your tracking isnt spot on.

The 70-200mm f2.8 IS (or atleast mine) is as almost as sharp at f2.8 as it at f10,

That shot was full frame was a tad long needed to zoom in a tad. Doing over 70mph they recon so the servo must be tracking pretty well.
 
Thanks for your replies.

Yup, two questions.

One of the problems with animals / dogs is the unpredicatably of movement – unless doing staged stuff. So keeping the AI servo tracking nicely is important. I’ve read that the high precision at 2.8 is good – but how good?

The 70-200 F4 L is a nice lens – and I wouldn't px it. But on duller days sometimes I just haven’t bothered taking a shot. I’ve got a 580 speedlite – but this makes everything a bit cumbersome. That extra stop of light might prove all the difference – but I guess the DoF might suffer a bit too?
 
Yeah check your DOF but also bear in mind that the smaller the DOF the longer the AF takes and the more accurate it has to be which is tough on a bouncing dog!... which is why I use F9(ish) for motorsport
 
If you want to see performance from a 40D and a 70-200 @ f/2.8, with a subject that is actually changing focal distance at a pace, then check out my post here....

http://forums.dpreview.com/forums/read.asp?forum=1019&message=28851629

I don't really understand why people post single shot examples of a subject moving across the frame as a demonstration of AF performance, since the AF has not got much work to do to keep up with the relatively small changes in focus distance. What you need is a subject with a high closing or retreating speed. The proof of the pudding is also in a consistent sequence, not one cherry picked example.

Here are the specs from the 40D white paper....

Compared to the EOS 30D, the EOS 40D’s focusing calculation
speed is 1.3 times faster, and the AF data-processing time is
shorter. Predictive AF can track a subject approaching at 50
kph/31 mph up to about 26.2 ft./8m away with an EF
300mm f/2.8L IS USM lens.
Click to expand...

Look at the Rob Galbraith tests on the 1D3 - a runner coming head on straight towards the camera! It's that sort of test that is required, not a subject with only minor changes in distance over time.
 
Yes, its to do with relative position change not actual speed... which is what people always get wrong. My 30D is only rated at the same 31mph but that doesn't mean I can't take a sharp photo of a 200mph superbike, just that if its head on at 200mph, it can't keep up!

It *might* work, but your hit rate will be random!

It does work reasonably if you wait till the bike brakes and turns in, ie both slows down in terms of its own velocity and when it turns actually slows the relative velocity OR you pan a subject moving across in front of you when the rate of relative velocity is inside the 31mph limit.
 
Actually, if the superbike, or even a military jet, is far enough away, then your AF will be just fine, as the focus adjustments required to keep tracking the subject will be tiny. The going only gets tough as the subject becomes fairly close and the AF has to adjust the lens more rapidly to keep up. You'll also have a whopping DOF at greater distances so marginal focus errors will be less obvious. In fact, you can pretty much photograph planes without AF at all - just set the lens to MF at the hyperfocal distance and off you go.

Focus with a 40D at 200mm and f/8 at the hyperfocal distance (263.4m) and you'll keep everything acceptably sharp between 131.7m away and infinity, without any need to touch the focus further. I doubt many public displays of jets wolud have the aircraft closer than 130m to the spectators. Check out the hyperfocal distance here....

http://www.dofmaster.com/dofjs.html

The reason Canon quotes a speed and a distance at which that speed applies is because both are important elements. Speed on its own is not relevant. Distance on its own is not relevant. It is the combination that counts. 400 mph would be fine for a subject 1/2 mile away, I'm guessing, and since the DOF at that distance would be huge I'm pretty sure I'm right..
 
Yes, that is also true, but usually at a circuit unless you have some sort of super mega piece of glass your engagement distances are quite short ;-)
 
If I had a 200 mph superbike coming straight towards me at a close distance I think AF performance would be the least of my worries :LOL:

I don't shoot a lot of motorsport, but my recollection from a recent visit to Silverstone with my 40D and 100-400 is that there were pretty long run-offs at the end of long straights and it would be impossible for Joe Public, such as me, to get very close at all to an oncoming vehicle at high speed. Here's an uncropped shot at 400mm. I would not call that a very close vantage point. Sorry for the poor IQ - this was shot through safety fencing. I just posted it as an example of the distance away from oncoming traffic, not passing traffic, that was typical of the circuit.

20080608_134039_4949_LR.jpg


It's true that people beside the straight are fairly close to the cars but only as they go past, not as they are approaching. In fact, if you tried to aim the camera up the track towards the high speed oncoming traffic all you would get is an eyeful of fencing, as the perspective closed up the gaps in the mesh.
 
tdodd said:
If you want to see performance from a 40D and a 70-200 @ f/2.8, with a subject that is actually changing focal distance at a pace, then check out my post here....

http://forums.dpreview.com/forums/read.asp?forum=1019&message=28851629

I don't really understand why people post single shot examples of a subject moving across the frame as a demonstration of AF performance, since the AF has not got much work to do to keep up with the relatively small changes in focus distance. What you need is a subject with a high closing or retreating speed. The proof of the pudding is also in a consistent sequence, not one cherry picked example.

Here are the specs from the 40D white paper....



Look at the Rob Galbraith tests on the 1D3 - a runner coming head on straight towards the camera! It's that sort of test that is required, not a subject with only minor changes in distance over time.
Click to expand...

This better for you? 2 consecutive shots, the second has a minor crop to remove gap behind the rider. There was 4 or 5 if you want more?


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Its not perfect, but the 70-200mm f2.8 is lightning fast on the 40d, its a hell off alot faster then the 30d i used to use it on.
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