is AI servo less accurate than one shot?

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Whenever I have tried AI Servo mode even on a subject that isn't moving, I never get as good focus as when I choose one shot focus, is this because servo isn't as accurate or am I just doing something wrong?
 
you don't use AI servo for static subjects, just like you don't use IS on a tripod. It will try to detect movement that isn't there and will not be as accurate as one shot.
 
well i know servo is for moving objects but when static it is sharper than when moving, in general i dont find servo to be very accurate at all, i dont get anywhere near the results i get from one shot. Should I be able to get sharp focus on a slow moving object from servo or am I just expecting too much?
 
trencheel303 said:
just like you don't use IS on a tripod. It will try to detect movement that isn't there and will not be as accurate as one shot.
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this is not true of later models may be on early ones or non Canon.

As for the AI servo focus have you get it set on auto focus point?
Watch this video you see all what you want is at 3:00
And this one as well is good it shows you how
 
Chaz Photos said:
this is not true of later models may be on early ones or non Canon.
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I was fully aware of the fact that some of Canon's latest lenses have tripod sensing IS, but other lenses don't, and the general idea with IS is turn it off when on a tripod. I was kinda hoping someone wasn't going to split hairs on that fact but there's always one... ;)
 
trencheel303 said:
I was fully aware of the fact that some of Canon's latest lenses have tripod sensing IS, but other lenses don't, and the general idea with IS is turn it off when on a tripod. I was kinda hoping someone wasn't going to split hairs on that fact but there's always one... ;)
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Facts are facts, the only reason to turn it off is to save battery.
 
Chaz Photos said:
Facts are facts, the only reason to turn it off is to save battery.
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I'm not sure there is any such thing as tripod sensing. It certainly doesn't turn the IS off automatically in any way, nor does it park it. I have two Canon IS lenses, both new and recent models - 24-105L and 70-200L 4. For sure the 70-200 has got Canon's latest and best 4-stops IS mech.

The handbooks for both lenses say turn the IS off when on a tripod and for bulb exposures, warning that it may "introduce errors".

And sure enough, if I put the lens on a tripod, IS on and in live view with max magnification, you can see the image drift very very slightly to and fro.

It's nothing like my 100-400L was, with its old IS that used to wander all over the place, but it still moves.

I think tripod sensing is marketing-speak for very low noise circuitry that doesn't build up excessive feedback between the IS gyros and motors, but there's still some residual noise and movement, so you should always turn it off on a solid tripod.

Edit: have you seen any reference to tripod sensing in any official Canon documents? I'd really like to see what they say.
 
trencheel303 said:
you don't use AI servo for static subjects
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Can I split hairs on that one too? Maybe it's a Canon issue, but I've never had a problem using continuous servo AF on my D200 or D300s with static objects.

Do the Canon bodies not have several different AF modes for using continuous servo AF mode? On my D300s there's 3 different modes.

1) Let the camera pick the AF point(s) based on nearest subject or facial recognition.

2) Manually pick a single fixed static AF point and it continues to monitor that AF point on a half-press, even if you move the camera around and what's in front of that AF point is no longer your subject (although it does have some degree of "intelligence" for subjects that become temporarily hidden and holds the correct focus, eg. somebody walks past in front of your subject).

3) Manually pick a single AF point, put that over your subject, half press and it'll track your subject even if it moves about the frame (so you can recompose or for tracking moving subjects) <-- which is what I'd use for shooting static objects hand-held if I wasn't in single servo AF mode.
 
The 55-250 has that feature too. I was panning with it at Goodwood in the weekend and also just ended up turning off IS. The danger is though, that you can forget to turn it back on again like I did! :bonk:

I was using Al-Servo for panning shots and the success rate for me was very low, so I switched back to one-shot.

I guess essentially a panning shot is really more of a static shot as you are moving the lens to be at the same speed of the car?
 
Usually Canon's AI Servo AF is just fine for static subjects and, being the lazy type, I will often use back button AF to simulate One Shot focusing even in AI Servo mode. The results are perfectly acceptable. Of course, with the 7D you have the option to have a quick flip from AI Servo to One Shot, and vice versa, by setting up the DOF button (as I have done) to temporarily switch AF modes.

While that facility is useful, I don't often feel the need to use it, but if I have a tricky focusing challenge, for a static subject, then I will switch to One Shot mode. The benefit of One Shot mode is that it is not under the pressure of time to keep looking for the next subject position, and it spends a fraction longer collecting image contrast data and working out what needs doing. In low light photography, like wedding services, One Shot can work where AI Servo simply will not. In good light, AI Servo is usually perfectly good enough.
 
thanks all, i think I have understood it better now, perhaps my issues was that I didn't realise auto focus point selection was needed for a moving object where you wanted servo to track it itself, also i have found switching to back button focus helps considerably for this mode
 
i've had the same experience as Tim.

on my 5D2, i found ai servo to be as accurate as one-shot in many cases, even at f2 on my 135.

i think i've said before, i actually use ai servo in many situations where you'd use one shot simply because it automatically compensates for minute movements of either me or the subject and with narrow dof this makes all the difference.

but also, like Tim says, sometimes ai servo gets confused by complex/fine patterns and low contrast and in those situations i need to use one shot.

but ai servo on my 5d2 will easily keep up with the erratic movements of a 20 month old child, many of the shots i've posted on the people and portraits forum were all taken using ai servo and using the out focus points.

i don't find the outer focus points as accurate as the centre point in any drive mode (i've noticed that it will sometimes front focus slightly), but i will say my keeper rate is about 70-80% with the outer points which isn't bad.
 
I rarely take my camera off A1 Servo whether I'm shooting moving subjects or still ones. It has huge advantanges over One Shot, in that it's continually making small adjustments for both your own and the subject's movement.

Something to be aware of when shooting in Onn Shot mode is that as soon as that focus confirmation light comes on - the focus is locked! That's stating the obvious I know, but you only have to hold that half-pressed shutter position for a fraction too long, for your own and/or the subject's tiniest movements to throw you out of focus - particularly at large apertures. You can only really trust that confirmation light at the instant it comes on and the shot should be taken as quickly as possible.
 
I shoot in AI servo just about all the time including static subjects. I also use the AF-ON button to focus and not the shutter button - doing it this way you can just pump the focus on and off which gives you a 'one shot' type focus if you want even when you are in servo mode.

For Birds I find this far better than one shot as even seemingly static birds can move slightly and the servo will keep the focus. The other big advantage is that if flyer suddenly comes along you are all ready to track via AI Servo.
 
A cheaper lens compared to a more expensive lens can give a bit of delay when AF-servo. The difference between the Tamron 70-300 and Canon 70-200 was night and day. The Tamron just couldn't keep up with movement and lots of shots came out oof. As soon as I tried the Canon, all the same type of shots came out as crisp as you like.
 
I mainly use AI Servo and back button focussing, which I prefer to using the shutter button. Simple and effective.
 
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