AI Focus vs AI Servo

[mdao]

Hi,

It seems the "AI Focus" does not work at all. It suppose to swicth between "One Shoot" and "AI Servo" if the subject start to move. When subject move, it does not refocus (when it refocus, you can see the lens start to move, it make some noise)

I test the "AI Servo" for moving objects and it work as advertised. Does anydody experience this problem, and if it does not work, why this mode ("AI Focus") exists?

Is canon going to fix it in the next firmware ?

[CyberDyneSystems]

I have had it "sort of" work a few times,. but not often. Certainly when you shoot a burst of shots,. that is when it "Should" workm,.. but alas just today I was shooting a White Heron taking off andd flying and it never refocused during all seven shots. Only the first two pics were in focus as it had not taken off yet. :(

Other times I will have the camera focused on a stationary object and it will suddenly decide that it needs to go into servo mode?

I agree it needs work !

[Persio]

CyberDyneSystems wrote:
I have had it "sort of" work a few times,. but not often. Certainly when you shoot a burst of shots,. that is when it "Should" workm,.. but alas just today I was shooting a White Heron taking off andd flying and it never refocused during all seven shots. Only the first two pics were in focus as it had not taken off yet. :(

Other times I will have the camera focused on a stationary object and it will suddenly decide that it needs to go into servo mode?

I agree it needs work !

I have used it successfully.
The problem may be switching the focus function on and off by releasing and pressing the shutter button between shots while the object is moving.
Try setting C.Fn-4=1. Press the * button to lock focus on the subject and keep it pressed as you follow the subject's movement with the camera and shoot your pictures as you please during the action. If you have selected the central focus point, make sure you keep the object within its area of influence or else the camera will loose it.
Give it a try and let us know if it works...

[Digital Don]

I'v done some subjective focus mode testing on airplanes landing at a local airport.

I took 20 pictures using AI Servo and 20 more using AI Focus. Canon 10D, Canon 28-135mm (IS turned off).

Here are my results:

AI Servo - 15 of the pictures were sharp, 4 were acceptable, and 1 was poorly focused.

AI Focus - 10 pictures were sharp, 6 were acceptable, and 4 were poorly focused.

These results were similar to my D30 in AI Servo mode. And, of course some lack of focus may be caused by camera shake.

In the current implementation of AI Servo in the 10D, you get a 'negative confirmation' (a blinking light and the shutter will not fire) if the camera has not achieved focus. However, I wish Canon had activated the 'focus confirmation light' or beep in AI Servo mode.

Yesterday I sent an e-mail to Canon with that exact suggestion for a future firmware update.

No response yet. We'll see what happens. In the mean time, I'm using AI Servo.

Digital Don
just plane pictures
http://members.aol.com/dg247

[CyberDyneSystems]

Persio,

I think you may be on to some of my problem, at least with the heron today.

I have indeed selected the center AF point as default.

Perhaps If I had been fast enough to hit the * button which on my Camera's custom functions will enable all 7 AF points, I would have gotten more pics in focus.

It will be while for me to get the hang of this camera for sure. Thanks for the tips.

[robertwgross]

Which camera are you discussing?

---Bob Gross---

[dcchan2]

Digital Don wrote:
I'v done some subjective focus mode testing on airplanes landing at a local airport.

I took 20 pictures using AI Servo and 20 more using AI Focus. Canon 10D, Canon 28-135mm (IS turned off).



My understanding is that to properly test AI Focus, you should be shooting airplanes taking off rather than airplanes landing.

AI Focus assuming that the subject is initially stationary and then starts to move after focus has been achieved.

[Digital Don]

dcchan2 wrote:

"My understanding is that to properly test AI Focus, you should be shooting airplanes taking off rather than airplanes landing."

There may be something to what you said.

Since I'm panning as the planes pass by, there is actually little relative movement between the camera and the subject. Maybe I'll repeat the test using the "One Shot" mode as well just to see how it works out.

Digital Don
just plane pictures
http://members.aol.com/dg247

[PacAce]

Digital Don wrote: Maybe I'll repeat the test using the "One Shot" mode as well just to see how it works out.


You have to be in AI Focus or AI Servo for the camera to track a moving subject. It won't do so in One Shot AF mode.

[CyberDyneSystems]

Bob,. I was dicussing the 10D,. I think we all are,. but then again,. ???? :)

[mdao]

Sorry, I was talking about the 10D, I did set the focus buuton to the *, and used center focus. I agree sometimes, it work, others it don't.

But if it's so unreliable, I can't trust it. But then i'm not the only one which have the trouble, so I think they can fix in the next firmware upgrade.

This is want I found out:

A) if you use the AI Servo and the subject move of of the DOF, it will refocus. You can hear the focus ring moving or even better go to breeze browser and look at the focus distance it changed from shoot to shoot if the subject has move out of the DOF

B) if you use AI servo, the focus distance stay the same (in breeze browser), or the focus ring is not or minimal moving


I may be wrong but if the subject move out of the original DOF, then it won't work. So it depend on the original DOF (which depend on the f-stop)

[PacAce]

Digital Don wrote:
In the current implementation of AI Servo in the 10D, you get a 'negative confirmation' (a blinking light and the shutter will not fire) if the camera has not achieved focus. However, I wish Canon had activated the 'focus confirmation light' or beep in AI Servo mode.


I guess I can see why Canon chose not to beep in AI Servo mode. It'd be beeping like crazy every time focus was achieved when you're tracking a moving subject.

I do agree with you that they could have at least kept the confirmation light turned on. However, the only problem with doing that is that the confirmation light would turn on as it acquired focus, then turn off as the subject went out of focus, and then turn back on again when focus is acquired again, etc. That'd be very confusing since a blinking confirmation light indicates that focus was NOT achieved, but in this case the opposite is true. ???

BTW, subject tracking in AI Servo and AI Focus seems to work fine with my camera although I just did a rudimentary test...I moved the camera instead of the subject moving but I would think the principal of operation is the same, no?

[Digital Don]

I received a reply from Canon. Apparently they do not intend to add the 'focus confirmation' light or beep to AI Servo mode.

In their reply they mention that they don't consider it a "malfunction". The manual mentions the fact that the light and beep do not work. My suggestion to them was to MAKE it work...

Oh well.

Digital Don
just plane pictures
http://members.aol.com/dg247

[photographer55]

Hi,

It seems the "AI Focus" does not work at all. It suppose to swicth between "One Shoot" and "AI Servo" if the subject start to move. When subject move, it does not refocus (when it refocus, you can see the lens start to move, it make some noise)

I test the "AI Servo" for moving objects and it work as advertised. Does anydody experience this problem, and if it does not work, why this mode ("AI Focus") exists?

Is canon going to fix it in the next firmware ?

I just stumbled onto this adn see in the manual that the focus will not reset unless the subject is opicked up on another of the AF squares.

[Yno]

I bet Canon has made some improvements in the eight years since the OP. :)

Welcome to the forum, photographer55!

[big_g]

I think the best advice is leave A1 Focus well alone. Stick with A1 Servo

Using back button focussing means you can very easily stop refocussing occurring just like 1 shot so you get the best of both worlds

[DutchVince]

I have no use for AI Focus.
I really wonder why this mode was created at all.

AI Servo works very well and seems to be faster.

[Waldemar Sikorski]

http://jefflynchdev.wordpress.com/2011/01/24/using-canons-ai-focus-mode-to-catch-the-action/

[DutchVince]

Since AI servo focuses well on stationary objects as well I use it most of the time.
As a bonus I don't get these annoying focus confirmation beeps :)

A quote from another forum sums it up quite nicely:

AI Focus is notorious for keeping One Shot when it should have shifted to Servo, and shifting to Servo when it should have stayed in One Shot. That's the reason why most people don't use it and why it's not available on the 1D series.

[hollis_f]

I hate to prolong this zombie thread, but...

One-Shot is for when neither you, or the subject, are moving or are likely to move.
AI Servo is for when either you, or the subject, is moving or is likely to move.
AI Focus is for when neither you or the subject care if your focus is accurate.

[blueM]

I hate to prolong this zombie thread, but...
One-Shot is for when neither you, or the subject, are moving or are likely to move.
AI Servo is for when either you, or the subject, is moving or is likely to move.
AI Focus is for when neither you or the subject care if your focus is accurate.


YES! bw!