A word about 10D AI Servo

[Pekka]

Hi,

I went out and took some time to find out more how 10D's AI Servo with ALL 7 focus points active really works. I really don't use that mode much but 10D's 7 points got me interested. Shot people walking, traffic. Weather was dull, overcast and sun was starting to set. I used 50/1.4 at 1/200 f3.5 and ISO 100-200. Focus lock assigned to * button.

My finding was that AI focus works exactly as manual says: CENTER focus point is used as initial locking point and subject in that area is followed by AI as long as focus is being locked (* pressed). Yep: center point, even if you have all points active. In any other case, when you do not give the camera any initial focus subject it focuses mainly where-ever it wants to. But if it is locked to certain subject it will not loose fix even if something passes in front of it.

This means that if you lock AI Servo focus (press * down and keep it down) to subject

http://photography-on-the.net/10D/focus/CRW_5045.jpg

and motorcycle drives in front of it, the focus stays on initial subject

http://photography-on-the.net/10D/focus/CRW_5046.jpg

to get motorcycle in focus, in previous case, you should have locked center point to cycle and let camera follow it.

This is how intelligent 10D gets when you show it the subject:

Focus is locked using center point (* pressed and kept down) in single shot mode.

http://photography-on-the.net/10D/focus/CRW_5050.jpg

Then you recompose, or keep camera as it is, it follows the subject

http://photography-on-the.net/10D/focus/CRW_5051.jpg

Take another shot (* pressed and kept down). Focus stays on subject even if it is covered by something else momentarily

http://photography-on-the.net/10D/focus/CRW_5052.jpg

And another shot (* pressed and kept down)

http://photography-on-the.net/10D/focus/CRW_5053.jpg

I tested this many times, and always I got subject in focus and could recompose freely in certain limits (focusing point coverage) while 10D kept focus locked just fine.

[brian304]

ok so if you use Servo mode do you just hold down shutter half way or must you use the *.
Coming from Nikon this is all very complex for my small grey matter.
Brian

[mdavids]

brian304 wrote:
ok so if you use Servo mode do you just hold down shutter half way or must you use the *.
Coming from Nikon this is all very complex for my small grey matter.


Brian, that all depends on how you have Custom Function 4 set. Pekka has it set to use * for AF Lock. If you haven't messed with CF4, just press the shutter down like you normally would.

[Pekka]

Yes, sorry for confusion - I always keep Custom Function 4 at 1 which means focus is assigned to * button.

[brian304]

Pekka wrote:
Yes, sorry for confusion - I always keep Custom Function 4 at 1 which means focus lock is assigned to * button.
Thanks Michael and Pekka. ok I just need to go out and find some cars or people to shoot.
take care
Brian

[mdavids]

Pekka wrote:
Yes, sorry for confusion - I always keep Custom Function 4 at 1 which means focus is assigned to * button.

No confusion here - I'm a big CF4 fan as well!

Great test, by the way. Very helpful. Next you need to try an AI Focus test!

[plato]

Hi everyone,

I've assigned the * button to lock focus as well, and I'm not 100% sure, but I don't think you have to keep the button held down in AI servo mode to keep the subject focussed.

I just hold the * button down initially until it locks onto the target. From there on, the camera seems to continue tracking the subject on it's own, and I only need to use the shutter button to shoot without worrying about the focus. I tried this by locking onto a moving car in front of mine and the shots seem to be in focus.

Can anyone verify my observation?

[Slow]

Pekka....What the bleedin 'ell is that tracked vehicle in the first two images?

[Pekka]

plato wrote:
Hi everyone,

I've assigned the * button to lock focus as well, and I'm not 100% sure, but I don't think you have to keep the button held down in AI servo mode to keep the subject focussed.

I just hold the * button down initially until it locks onto the target. From there on, the camera seems to continue tracking the subject on it's own, and I only need to use the shutter button to shoot without worrying about the focus. I tried this by locking onto a moving car in front of mine and the shots seem to be in focus.

Can anyone verify my observation?

Maybe you're using CFn-04:02? CFn-04-01 needs keeping * down, with CFn-04:02 * acts ast focus lock button.

[martcol]

Slow wrote:
Pekka....What the bleedin 'ell is that tracked vehicle in the first two images?

Looks like a mobile bread maker - no, wait a minute, is it a DOF generater?

[martcol]

Oh, & Pekka, Very convincing test.

Must admit, I only use the centre focus point, 1/2 press shutter release & recompose. I don't like having all 7 focus points active because it confuses me. I'd rather select.

Anyway, if you assign the * to lock focus, what difference does it make or, why do you do it? What happens to the shutter release then?

Martin

[Slow]

martcol wrote:
Slow wrote:
Pekka....What the bleedin 'ell is that tracked vehicle in the first two images?

Looks like a mobile bread maker - no, wait a minute, is it a DOF generater?



I'll bet it would have been useful in Iraq!

[plato]

Pekka wrote:

Maybe you're using CFn-04:02? CFn-04-01 needs keeping * down, with CFn-04:02 * acts ast focus lock button.


That's strange, I'm using CFn-04:01.... I'll try it with more moving objects and see what happens. Perhaps I'm mistaken after all. Thanks!

[plato]

martcol wrote:
Oh, & Pekka, Very convincing test.

Must admit, I only use the centre focus point, 1/2 press shutter release & recompose. I don't like having all 7 focus points active because it confuses me. I'd rather select.

Anyway, if you assign the * to lock focus, what difference does it make or, why do you do it? What happens to the shutter release then?

Martin

With the * button assigned to lock focus, the shutter release button handles exposure and shutter release, ie you can manually focus the shot and press the shutter release button without the autofocus kicking in and overriding your manual focus at inopportune moments. It was a little confusing at first, but now that I'm used to it, I can't live without it!

[maxrebo]

I assume that if you have the 10D set to use only center AF point, then you lose the ability to recompose (since the other AF points are supposedly offline).

Is this accurate? Or is the 10D smart enough to use all AF points to track in AI Servo even if you set only center AF point active?

So lets say someone normally shoots in One Shot focus with center AF point only. In order to track objects, he would have to quickly switch to AI Servo focus and turn on all 7 AF points. Right?

Just wondering. Thanks.

[tony723]

In your example photo of people, it means when the subject moving fast it is still in focus?

[jimwong]

Great info Pekka

I was shooting in 1 shot mode with all 7 AF points active indoors at a fashion show with a 420ex flash. I was positioned in front and off to one side of the runway. Some shots were fine, others were not in focus. I was getting different AF points to light up and could not wait for the AF point I wanted or else I would lose the shot, so sometimes I'd get the face, or an arm or shoulder in focus.

I thought next time I'd shoot in AI Servo mode, with center AF point active. Can I pan with the camera once I get a focus lock or do I need to hold my position and hope she stays in the frame for AI Servo mode to work?

What do you suggest ?

[Slow]

jimwong wrote:

others were not in focus. I was getting different AF points to light up and could not wait for the AF point I wanted or else I would lose the shot, so sometimes I'd get the face, or an arm or shoulder in focus.

what do you suggest ?




I do not mean to sound flippant but what is wrong with using manual focus?

[jimwong]

manual focus is always an option, but I wanted to see what others thought about the options available and if I'm using them the best way on the 10d, aside from manual.