How to disable the focus on shutter button on the 5D MkIII if depressed halfway

[JerryKnight]

A bit off topic, but if you had an option for button on the front under the natural positions for your middle finger and ring finger, would you prefer the focus button was there?  Maybe its the video gamer in me, but I feel like those fingers are just hanging around, waiting for something to do.

Maybe, but for me, the non-index fingers are for support and the thumb's natural position goes over the back AF button. I suppose the same could be said about the thumb being for support, but I use the heel of the thumb and the lower fingers to firmly grasp the camera, leaving the index finger free to shoot and the tip of the thumb free to push the AF button. Again, it's a matter of personal preference.

I checked, and the DOF button cannot be set to AF start, only AF stop and other non-AF functions. So we can't really experiment with it.

[Autocall]

Here's an article on Canon DLC RE: "back-button autofocus explained".
http://www.learn.usa.canon.com/resources/articles/2011/backbutton_af_article.shtml

KARMA +10!!!
what a prolific day...

[mcintoshi]

Again, I'm really keen to try this so thanks for the info folks.  Like some others I'm still waiting for my 5D3 to arrive so the query below is pure speculation

One other thing I've been reading about is activating the DOF button to jump into AI Servo mode (while it's pressed).  And I guess with AI servo you want to have your focus button continually down also, so that would mean to continually track the subject you'd have to simultaneously hold down all 3 buttons: your back button for focus, the DOF to stay in servo, and the shutter to fire.  Seems like a fairly convoluted configuration. 

Have I got something wrong with that logic?  Is there an easier way to somehow jump into servo mode quickly without going thru the menu?  Is it possible to have the focus button when continually held down somehow know that it's in servo mode?

[idratherplaytennis]

Quick related, semi-related question about this focus disable and the metering settings. I'm still learning, and used to a 20D, but I'm getting more serious into this but had a quick question. I normally would shoot full manual on my 20D and I had to control everything, the exposure, shutter, iso and all that- like you all probably know, and I made the jump to the 5D3 and have been doing what reading and learning I can however one thing I'm in the dark about or just not getting is the metering part.

Why would I want to leave metering on during the 1/2 shutter depression? From my understanding, metering is the camera sensing how much light is coming in, balancing the scene if you have auto iso enabled and if you focus, recompose, but in doing so, if you re-meter the central area of the image (or does the metering just work for the whole image...?) isn't there the chance to throw off what you wanted the prime focus to be?

Hopefully someone can help me out here, I'm pretty confused and not even sure I stated my question correctly ><. Just trying to understand this whole Auto ISO (when enabled), metering, AF and AE buttons on the back of the 5D3 and all of that to better take advantage of the camera. If someone has a question for clarification of what I mean, I'll try and respond as soon as I can. Until then- dinner Thanks for any help you can provide!

[D.Sim]

Quick related, semi-related question about this focus disable and the metering settings. I'm still learning, and used to a 20D, but I'm getting more serious into this but had a quick question. I normally would shoot full manual on my 20D and I had to control everything, the exposure, shutter, iso and all that- like you all probably know, and I made the jump to the 5D3 and have been doing what reading and learning I can however one thing I'm in the dark about or just not getting is the metering part.

Why would I want to leave metering on during the 1/2 shutter depression? From my understanding, metering is the camera sensing how much light is coming in, balancing the scene if you have auto iso enabled and if you focus, recompose, but in doing so, if you re-meter the central area of the image (or does the metering just work for the whole image...?) isn't there the chance to throw off what you wanted the prime focus to be?

Hopefully someone can help me out here, I'm pretty confused and not even sure I stated my question correctly ><. Just trying to understand this whole Auto ISO (when enabled), metering, AF and AE buttons on the back of the 5D3 and all of that to better take advantage of the camera. If someone has a question for clarification of what I mean, I'll try and respond as soon as I can. Until then- dinner Thanks for any help you can provide!

I think the way it goes is the camera is always metering - sensing how much so it can go off on a moments notice, but when you depress the shutter, it stays at that setting ready to click off.

I could be wrong though, if I am, please do correct me