310D Users (hacked firmware AF question)

[Kabz]

What are the uses of the different AF's?
I think I understand AI servo, but can someone explain to me what they all mean and the specific uses for each setting and when its best to use which one and when to not use one?

Thanks.

[c0ntr0lz]

makes the brian think a bit faster or focuses on objects quicker

[DReb-MO]

This might clear it up.

There are three AF modes: One-Shot, AI Servo with predictive AF, and AI Focus. In One-Shot AF, the camera focuses on whatever falls under the active AF point, then locks focus there until you either take the picture or let go of the shutter button; and you can't take the picture until the camera has focused on something. In Predictive with AI Servo AF, the camera focuses continuously on whatever falls under the active AF point, you can trip the shutter at any time. In AI Focus AF, the camera automatically selects One-Shot or AI Servo AF to suit the shooting situation.

Of course, you can also focus manually, by moving the AF/MF switch on the lens to MF and rotating the lens's focusing ring until the image appears sharp in the viewfinder (with Canon USM lenses, you don't even have to switch to MF first). If you hold the shutter button halfway down as you focus manually, the in-focus indicator will glow when focus has been achieved, the AF point will flash, and the audible signal will beep (if you haven't deactivated it), just as they do when focus has been established in AF mode.

[Jon]

. . .
Of course, you can also focus manually, by moving the AF/MF switch on the lens to MF and rotating the lens's focusing ring until the image appears sharp in the viewfinder (with Canon USM lenses, you don't even have to switch to MF first). . .

Make that "with some USM lenses . . . " Try it with, say, the 28-90 USM 3 and you're going to have trouble autofocussing until you shift the lens back into manual and run it through the range, not to mention the grinding you'll give the gears. Someone (sorry, I bow to your expertise, but I can't remember where the post was to check your name) said that it's only the lenses with the Ring USM motor that can be manually focussed while in auto mode.

[roanjohn]

The only thing that won't work with the hack is the full time ai-servo.

ai-focus was our only option with the original firmware..........but now we are given one-shot focus (meaning you can lock focus and recompose without getting the dreaded OOOFFF!!!)

Ro1

[till]

With a tirck you can also use Servo AF: Switch to Servo AF. Point at the subject and have a finger at the AF/MF switch of the lens, but keep the switch on AF. Fully press the shutter button, the shutter will not release, but the camera will continuously focus. Keep the active focus point on the subject and wait for the right moment keeping the shutter button fully pressed. To take the shot switch to MF while keeping the shutter button pressed and the camera shoots immediately. So you shoot with you left hand by pulling the MF/AF switch to the camera's body. Before pointing onto the subject for the next shot, do not forget to switch the AF/MF button back to AF.

Till

[Kabz]

thanks for the good replies...
I think I'm starting to get it now...

[Guillermo Freige]

OneShot AF mode also enables the use of FTM (full time manual) lenses. FTM is the ability of Ring USM (or Sigma HSM) lenses to focus manually after AF lock. When you try to do that using AI Focus mode, the defocusing will trigger the lens to continuous focusing mode, so it`s useful as an "Pseudo AI Servo" mode in unmodified Rebels, but it renders useless the original use of the feature.