autofocus on 10d

[Osmer_Toby]

this is gonna sound like a really stupid question, especially coming from a supposedly semi-experienced photog, but here it goes:

how does af work on 10d? do you not have to hold down the shutter button half-way to initiate af? and does the focus remain static if you achieve focus and then let go, such that any movement towards or away from lens will render subject out of focus again? i'm talkin single shot full manual mode...

reason i asked is because i watched the school photogs come in and student after student sat on a stool, the "photog" did not touch the shutter button until ready to take the shot. i asked about this, and she said the cam, a 10d, was set on autofocus :scratch:

 

[mrsid99]

If it's on autofocus the shutter won't fire until it's focused.

 

[Osmer_Toby]

If it's on autofocus the shutter won't fire until it's focused.

but does it need to achieve a new lock for each subject/exposure? i.e. is the focusing dynamic, or static unless the shutter button is pushed halfway?

 

[mrsid99]

If it's on autofocus the shutter won't fire until it's focused.

but does it need to achieve a new lock for each subject/exposure? i.e. is the focusing dynamic, or static unless the shutter button is pushed halfway?

I guess the answer is both, in autofocus and one shot condition the camera tries to achieve focus lock and as soon as it has it then allows the shutter to fire.
If you pick up the camera (set on autofocus of course) point it at the subject and press the shutter button all the way down it obviously passes through the half down position at which time the camera tries to find focus and as soon as it achieves lock the shutter will then fire.
If you point the camera at the subject and press the shutter button half way and hold it there (one shot condition only) the focusing will then try to lock and once it has focus lock it remembers so long as you continue to hold the button half way. If you then point at something else (still holding the button half way) then the shutter will fire as soon as the button is fully depressed even though that whatever you're now pointing at may be out of focus.
For reference, there is also an "AI" setting for auto focus and in this condition the camera continuously tries to focus, even in the half way position, and again the shutter won't fire until it achieves lock, very useful for situations like sporting events.

 

[GerryDavid]

Maybe he set the lense up to have the subject in focus and turned manual focus on so it doesnt go through the focusing each time. If the subject is in the same area for every picture, you dont need to focus each time. Assuming your not using F4 or smaller. Its my understanding you use F8 for portraits which has some give on dop.

 

[mrsid99]

Maybe he set the lense up to have the subject in focus and turned manual focus on so it doesnt go through the focusing each time. If the subject is in the same area for every picture, you dont need to focus each time. Assuming your not using F4 or smaller. Its my understanding you use F8 for portraits which has some give on dop.

I doubt it, the autofocus on the 10D is extremely fast assuming reasonable light levels.
The focusing starts from where it was from the previous shot so assuming the focusing hadn't changed that much you probably wouldn't even notice the delay.

 

[photogoddess]

With the 10D you can also set up in the custom functions menu separate focus and ae/lock buttons.

 

[markc]

With the 10D you can also set up in the custom functions menu separate focus and ae/lock buttons.

That's how I use mine. I first learned about it on the EOS 5 (A2e). Pressing the * button will focus (how it focuses is based on the focus mode), and the shutter button holds exposure while half-pressed and triggers shutter when fully pressed. It's a great custom fuction once you get used to it.

You can focus with *, recompose, then hit shutter as many times as you want without the camera refocusing.

 

[Osmer_Toby]

With the 10D you can also set up in the custom functions menu separate focus and ae/lock buttons.

That's how I use mine. I first learned about it on the EOS 5 (A2e). Pressing the * button will focus (how it focuses is based on the focus mode), and the shutter button holds exposure while half-pressed and triggers shutter when fully pressed. It's a great custom fuction once you get used to it.

You can focus with *, recompose, then hit shutter as many times as you want without the camera refocusing.

actually, that is exactly how i have mine set up. i still find myself having focusing problems of varying degrees, tho. e.g. i have a real hard time getting it to achieve focus lock when working with a softbox and modelling lights only. it seems the light ought to be enough from the modelling lights, but i can't get the damn thing to focus. do i need brighter modelling lights or sumthin wrong with the cam or is it still me? it's drivin me nuts!!

 

[DocFrankenstein]

the "photog" did not touch the shutter button until ready to take the shot

It takes less than a second to focus, so that's not a problem. The cam focuses when the shutter button is half pressed.

There are 3 focus modes to focus on 10D:

1) One shot:
The camera has to lock and focus before you can take a shot. Once locked, the focus point doesn't change.

2) AI Servo
You can release the shutter any time. The camera hunts for best focus all the time. Designed for moving stuff.

3) AI Assist
The camera (supposedly) intelligently chooses whenther the object is moving or is static and goes from there.