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

[wickidwombat]

How is the back-button focus any different than pressing the shutter button halfway on subject, composing your shot with, then depressing fully??

Ok here goes

Situation 1 - shooting in a studio narrow aperture your distance to the subject not changing much you can focus onece then just shoot without having to keep refocusing if you are not moving, if you change position or distance you can focus again then shoot off a few shots.

Situation 2 - Shooting in AI servo you just hold that button down the whole time to make sure it holds tracking and press the trigger when you want (its much much better than the half pressing).

Situation 3 - Landscape on a tripod, frame the shot focus using the back button recompose to suit and now you can shoot at will without it trying to refocus on something

Situation 4 - use AF to aquire the target then MF to refine in this case hitting the shutter button doesnt try to refocus.

There are probably more but those are a few handy situations.

 

[JerryKnight]

How is the back-button focus any different than pressing the shutter button halfway on subject, composing your shot with, then depressing fully??

The specific benefits are a matter of personal preference, but the overall philosophy is that the shutter button should not be controlling the autofocus. It's combining two things that need not (and should not) be combined. But this opinion usually comes from people (like myself) that shoot mostly manual and demand complete control over all aspects of the camera in any order.

For me, the separation of which finger does what is the biggest benefit. I am a very manual person, and I like having each finger on the camera perform one function at a time. Once the exposure is set, the index finger's only purpose is to fire the shutter. This helps me a lot with timing.

The other main benefit for me is immediacy. With back-button focus, the shutter button will always fire the shutter (assuming you release the AF button - it can still be delayed if you're holding down the AF button). When you've set the focus and are waiting for the shot, you don't have to worry about the half-shutter refocusing.

Simply put, there are several situations where half-shutter focus is not ideal. There are arguably no situations where back-button focus is not ideal (pardon the double-negative).

 

[prestonpalmer]

Just about EVERY professional photographer I know uses the thumb focus, shutter AE lock method. I learned this WAYYY back from a National Geographic Photographer when my Canon 10D was the hottest camera on the block. It took me about a week to get use to it, and Ive never looked back. I can honestly say that this one little change in my shooting style has attributed to my success as a photographer more than anything else I've learned. Everyone who comes to my photo-classes or apprentice program is shown this, and encouraged to use it. I don't know anyone who goes back to the default method after using and understanding the power of this. One of these days I am going to make a video tutorial on how this works in the real world, and why it is such a powerful method to adopt for your photography.

 

[Autocall]

C. Fn 2, Custom Controls, set the first option (shutter button) to either "Metering Start" or "AE Lock".

This was among the very first things I did to the 5D3 when it arrived. The whole point of back-button focus is to separate the focusing from the shutter activation. The AE Lock (on shutter half-press) is handy when shooting Av/Tv because you can focus on one point, meter on another, recompose, and activate the shutter independently. Total control.

Edit: I just saw how Canon chose to abbreviate the setting name.. "Shutter Butt. half-press". Really, Canon? There's no other way to abbreviate "button"?

wow! +5 karma

 

[MasterJul]

I like to use it "the other way", use the AF back button to... stop the AF.

When I want to shoot squirrels in the trees, it's pretty hard to focus on the subject moving quickly throught the branches and when the focus is locked, I need an instant shoot. That's a situation where I think it's easier to have AF + shoot on the same button: quick focus lock and shoot.

When the subject is frozen and I have time to stabilize myself and the camera, or when I wish to use manual focus because it's almost impossible for the camera AF to reach the subject, I keep my thumb on the AF back button and shoot.

Do you think I'm wrong and would it be better to use the AF back button for dedicated focus? Thanks for your feedback.

 

[PhotoGib]

How is the back-button focus any different than pressing the shutter button halfway on subject, composing your shot with, then depressing fully??

The specific benefits are a matter of personal preference, but the overall philosophy is that the shutter button should not be controlling the autofocus. It's combining two things that need not (and should not) be combined. But this opinion usually comes from people (like myself) that shoot mostly manual and demand complete control over all aspects of the camera in any order.

For me, the separation of which finger does what is the biggest benefit. I am a very manual person, and I like having each finger on the camera perform one function at a time. Once the exposure is set, the index finger's only purpose is to fire the shutter. This helps me a lot with timing.

The other main benefit for me is immediacy. With back-button focus, the shutter button will always fire the shutter (assuming you release the AF button - it can still be delayed if you're holding down the AF button). When you've set the focus and are waiting for the shot, you don't have to worry about the half-shutter refocusing.

Simply put, there are several situations where half-shutter focus is not ideal. There are arguably no situations where back-button focus is not ideal (pardon the double-negative).

BIG thanks to you and others who have shed light on this technique. I'm looking forward to giving it a go when the mkIII comes tomorrow.

 

[idratherplaytennis]

As with so many of the previous posters who were unaware of the thumb-focus, index-fire method, I really feel a great desire as well to express my gratitude to informing us on the forum of this technique. I had never even thought that there might be another way to focus, recompose, fire, and frankly, it's annoyed me to no end at times, when I depress, recompose while holding the shutter decompressed and have to deal with a re-composition in this method like 5 times before I get it. Totally excited to try this new setting out when my 5D3 arrives on Thursday, and every other great benefit, upgrading from a 20D I purchased about 4-5 years ago. Still learning, but this hands down beats so much of what I have learned so far because it's really helpful. I'm about to look through the menu on my 20D to figure out how to switch that feature on (which if it was on a 10D as I believe I heard, it should be on the 20D as well, I'd assume).

I know I will totally love this feature because I'm a practical person and as it had been stated- to focus one way and then fire with a different button- that makes all the sense in the world. THANK YOU SOOOOO MUCH!!!!! (Now I just have to worry if my 5D3 is going to be tack sharp or one of soft batches warranting a swap, eep!!)

 

[JerryKnight]

... I'm about to look through the menu on my 20D to figure out how to switch that feature on (which if it was on a 10D as I believe I heard, it should be on the 20D as well, I'd assume)...

Did a quick search. Set Custom Function 04 to option 1. The * button will be your AF start and your half-shutter will be AE lock (which will do nothing in full manual mode, of course)

I started using this feature with my original Digital Rebel (300D). I think it even involved using a hacked 10D firmware on the 300D... That was a long time ago.

EDIT: Set it to option 3 if you want the half-shutter to do nothing, in case you shoot Av/Tv and don't want AE lock.

 

[CanineCandidsByL]

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.

 

[stakx]

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

 

[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