Re 70D and back button AF?

JohnLock · Nov 7, 2015

I'm a new 70D user and I almost always shoot in aperture preferred priority mode (Av). If I activate and press the back button AF does that then over ride AF when the shutter button is pressed?

This seems rather confusing to me, but what's been happening is I've been getting some really bad exposures as I presently just have AF and AE on the shutter button.

I would like to be able to focus then re-compose and get good exposures. What is the best way to do that-- or is it possible?

I have long used Olympus 4/3 and now m43 and this is not a problem as in the menus Oly lets you set AF and AE independent of each other with both on the shutter button, so that's what I'm used to. I've also used several Canon bodies from the 40D on but don't remember this being an issue.

I picked up the 70D because I really like the camera and I wanted to be able to use the excellent 15-85 lens for its sharpness and versatility.

edit: I've spent quite a bit of time in the instructions CD, but this part is not clear to me.

Thanks.

John

canonvaggio · Nov 7, 2015

JohnLock said:
I'm a new 70D user and I almost always shoot in aperture preferred priority mode (Av). If I activate and press the back button AF does that then over ride AF when the shutter button is pressed?

This seems rather confusing to me, but what's been happening is I've been getting some really bad exposures as I presently just have AF and AE on the shutter button.

I would like to be able to focus then re-compose and get good exposures. What is the best way to do that-- or is it possible?

I have long used Olympus 4/3 and now m43 and this is not a problem as in the menus Oly lets you set AF and AE independent of each other with both on the shutter button, so that's what I'm used to. I've also used several Canon bodies from the 40D on but don't remember this being an issue.

I picked up the 70D because I really like the camera and I wanted to be able to use the excellent 15-85 lens for its sharpness and versatility.

edit: I've spent quite a bit of time in the instructions CD, but this part is not clear to me.

Thanks.

John

In the custom controls menu, you need to remove AF from the shutter button. It will just start metering, and the shutter.

JohnLock · Nov 7, 2015

Canonvaggio; that sounds exactly like what I needed to know, so thank-you very much-- and also for the quick response. I'll try to find that in the camera menus.

Thanks. John

canonvaggio · Nov 7, 2015

JohnLock said:
Canonvaggio; that sounds exactly like what I needed to know, so thank-you very much-- and also for the quick response. I'll try to find that in the camera menus.

You're welcome. Here's the manual page.

05c110f8fc6c4dcda5318a415b758cf4.jpg.png

JohnLock · Nov 7, 2015

Canonvaggio; I really do appreciate your help, but I have not been able to activate the AF-ON button at all, and I don't know what FEL means, but I've been assuming Focus/Exposure Lock?

I've tried that to no avail. Sorry to be so dense, but could you please tell me which of the settings in AF-ON actually activates the AF-ON button?

I haven't found the right combination yet. Thanks again.

John

canonvaggio · Nov 7, 2015

JohnLock said:
Canonvaggio; I really do appreciate your help, but I have not been able to activate the AF-ON button at all, and I don't know what FEL means, but I've been assuming Focus/Exposure Lock?

I've tried that to no avail. Sorry to be so dense, but could you please tell me which of the settings in AF-ON actually activates the AF-ON button?

I haven't found the right combination yet. Thanks again.

John

Unless you've changed it, the AF-ON button starts AF by default. And FEL is Flash Exposure Lock.

To remove AF from the shutter button:

Menu > C.Fn.III > 4

The first control graphic listed is the shutter button, select it, then choose "Metering Start" for the operation.

JohnLock · Nov 7, 2015

I'll have a go at that. Thank-you again.

John

JohnLock · Nov 8, 2015

I had to bail out last night to watch a football game (American), but after was able to follow your directions carefully and was finally successful in getting the 70D 'back button focus' to work in conjunction with 'metering start' on the shutter button.

Getting that procedure to work in Av mode is a very big deal to me and I thank-you very much for your good directions, and even more for your patience. I am now a "happy camper";>)

John Lock

Thermidor · Nov 9, 2015

JohnLock said:
I had to bail out last night to watch a football game (American), but after was able to follow your directions carefully and was finally successful in getting the 70D 'back button focus' to work in conjunction with 'metering start' on the shutter button.

Getting that procedure to work in Av mode is a very big deal to me and I thank-you very much for your good directions, and even more for your patience. I am now a "happy camper";>)

John Lock

Hi John, I just upgraded to the 70D like two weeks ago, and am just getting used to having focus button at the back. I shoot entirely in manual, so I hadn't really benefited from it as much. Can you explain how or why having the focusing set to the back button instead of the shutter helps you more? Thanks very much in advance.

JohnLock · Nov 9, 2015

Hi Thermidor,

By default the 70D has both AF and AE on the shutter button e.g. 1/2 press of the shutter button does AF then full press does AE.

I shoot a lot of seascapes/landscapes (using Av mode) where I often want to place focus (AF) just a few feet in front of the camera. So, if I focus there-- say 5-10 feet in front of the camera-- but then raise the camera for a good composition, the foreground will be out of focus and also under exposed because the default AF/AE on the shutter button will over-ride my attempt at closer focus and the bright sky will usually dominate the exposure.

If I can set AF and AE independent of each other, I can focus wherever I want then recompose and get a proper exposure and desired DOF. In practice though I have to either use HDR or multi-shot bracketing to get decent exposures when shooting in the direction of the sun-- which I do a lot-- then combine the shots later. Five shots at 1/2 f-stop intervals is usually good. Also exposure compensation can be easily moved up or down as needed to get 5 useable exposures.

I'd post an example, but they're on my editing computer.

When you say you shoot in manual mode do you mean manual AF as well? That's a whole other discussion.

Happy shooting, and enjoy your 70D.

John

R2D2 · Nov 9, 2015

JohnLock said:
Hi Thermidor,

By default the 70D has both AF and AE on the shutter button e.g. 1/2 press of the shutter button does AF then full press does AE.

I shoot a lot of seascapes/landscapes (using Av mode) where I often want to place focus (AF) just a few feet in front of the camera. So, if I focus there-- say 5-10 feet in front of the camera-- but then raise the camera for a good composition, the foreground will be out of focus and also under exposed because the default AF/AE on the shutter button will over-ride my attempt at closer focus and the bright sky will usually dominate the exposure.

If I can set AF and AE independent of each other, I can focus wherever I want then recompose and get a proper exposure and desired DOF. In practice though I have to either use HDR or multi-shot bracketing to get decent exposures when shooting in the direction of the sun-- which I do a lot-- then combine the shots later. Five shots at 1/2 f-stop intervals is usually good. Also exposure compensation can be easily moved up or down as needed to get 5 useable exposures.

Manual Exposure Mode will solve the problem.

R2

R2D2 · Nov 9, 2015

Thermidor said:
I just upgraded to the 70D like two weeks ago, and am just getting used to having focus button at the back. I shoot entirely in manual, so I hadn't really benefited from it as much. Can you explain how or why having the focusing set to the back button instead of the shutter helps you more? Thanks very much in advance.

You first need to disassociate autofocus from the shutter button.

Then set the autofocus to AI Servo. I recommend using a single AF point.

Now you can focus on whatever you want, and then lock the focus when you lift your thumb from the back button. Focus will stay locked until you want to change it (no need to keep the shutter half-pressed to lock focus). And you don't need to wait for the AF to re-acquire (no lag). Just shoot shoot shoot. You can even chimp for a while in-between and the focus won't have changed.

It takes a while to get used to it, but once you start there's no going back.

Have fun,

R2

Thermidor · Nov 9, 2015

R2D2 said:
Thermidor said:

I just upgraded to the 70D like two weeks ago, and am just getting used to having focus button at the back. I shoot entirely in manual, so I hadn't really benefited from it as much. Can you explain how or why having the focusing set to the back button instead of the shutter helps you more? Thanks very much in advance.

Click to expand...

You first need to disassociate autofocus from the shutter button.

Then set the autofocus to AI Servo. I recommend using a single AF point.

Now you can focus on whatever you want, and then lock the focus when you lift your thumb from the back button. Focus will stay locked until you want to change it (no need to keep the shutter half-pressed to lock focus). And you don't need to wait for the AF to re-acquire (no lag). Just shoot shoot shoot. You can even chimp for a while in-between and the focus won't have changed.

It takes a while to get used to it, but once you start there's no going back.

Have fun,

R2

Thermidor · Nov 9, 2015

JohnLock said:
Hi Thermidor,

By default the 70D has both AF and AE on the shutter button e.g. 1/2 press of the shutter button does AF then full press does AE.

I shoot a lot of seascapes/landscapes (using Av mode) where I often want to place focus (AF) just a few feet in front of the camera. So, if I focus there-- say 5-10 feet in front of the camera-- but then raise the camera for a good composition, the foreground will be out of focus and also under exposed because the default AF/AE on the shutter button will over-ride my attempt at closer focus and the bright sky will usually dominate the exposure.

If I can set AF and AE independent of each other, I can focus wherever I want then recompose and get a proper exposure and desired DOF. In practice though I have to either use HDR or multi-shot bracketing to get decent exposures when shooting in the direction of the sun-- which I do a lot-- then combine the shots later. Five shots at 1/2 f-stop intervals is usually good. Also exposure compensation can be easily moved up or down as needed to get 5 useable exposures.

I'd post an example, but they're on my editing computer.

When you say you shoot in manual mode do you mean manual AF as well? That's a whole other discussion.

Happy shooting, and enjoy your 70D.

John

Hi John,

Thanks for your reply. I mostly shoot stage, where I need to spot meter in low light, so I can't really use aperture priority because I need to keep toggling the auto exposure lock with every shot, or the camera will change the metering settings when I recompose. It's for this reason I have to shoot entirely in manual.

In daylight or well-lit conditions, I can use evaluative metering instead where the camera isn't going to change the settings dramatically when I recompose in aperture priority mode.

I see how the back button AF can be useful now: effectively it means I can compose my shot first, and meter later instead of relying on the auto exposure lock. It take some getting used to, since I spent years half-pressing the shutter button.

Thanks for your reply, appreciate it!

Bramble9 · Nov 9, 2015

The possible combinations of AF, AE, Servo, MF etc. are almosy endless. I don't use manual focus anymore due to my aged eyes, so good AF is essential for me. Good discussion.

John

canonvaggio · Nov 10, 2015

JohnLock2015 said:
The possible combinations of AF, AE, Servo, MF etc. are almosy endless. I don't use manual focus anymore due to my aged eyes, so good AF is essential for me. Good discussion.

John

Multiple accounts are not allowed on dpr forums, JohnLock and JohnLock2015.

S Castle · Nov 10, 2015

You know, I had to scratch my head, get out the camera, and do a few checks. The way my camera works (and the way all my AF SLRs have worked) by default is: a half-press of the shutter starts AF and (if AF is set to one-shot) locks it, and also starts and sets AE. If I maintain the half-press while recomposing, both exposure and focus are maintained as they were at after I did the half-press (AF-lock and AE-lock). A full press then takes the shot. If I press the AF-ON button on the back and keep it pressed (again using AF one-shot) then the half-press of the shutter only sets exposure (for this both AF-ON is pressed and the shutter is half-pressed). So I don't really understand why decoupling AF from the shutter might be useful. Maybe if you use the other AF modes, AI Focus and AI Servo, then it might be important. I have found these not to be very useful, myself.

I am used to going full manual (both focus and exposure) because some of the landscape photos I take require that to turn out correctly (panoramas and very long exposures, for instance), and back in the pre-AF days it was of course the only way.

canonvaggio · Nov 10, 2015

scastle said:
So I don't really understand why decoupling AF from the shutter might be useful. Maybe if you use the other AF modes, AI Focus and AI Servo, then it might be important. I have found these not to be very useful, myself.

You only have half of the idea then. Yes you remove AF from the shutter button, but you also set the AF mode to AI Servo. The advantages are that you can now "focus lock" simply by removing your thumb from the AF-ON button at any time, you can remeter the scene without refocusing, and you can shoot still and moving subjects on the fly without changing AF mode.

The main disadvantages (IMO) are: you lose the focus confirmation beep and red AF point light of Single Shot, and the AF-ON button itself is quite small and has a relatively long travel. I find the thumb movement quite awkward.

This sort of ties into a post today in the Open Forum by the Camera Ergonomics blog guy. His idea is that ergonomics is all about the fewest actions (hand and finger movements) needed to accomplish the task.

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Thermidor · Nov 10, 2015

scastle said:
You know, I had to scratch my head, get out the camera, and do a few checks. The way my camera works (and the way all my AF SLRs have worked) by default is: a half-press of the shutter starts AF and (if AF is set to one-shot) locks it, and also starts and sets AE. If I maintain the half-press while recomposing, both exposure and focus are maintained as they were at after I did the half-press (AF-lock and AE-lock). A full press then takes the shot. If I press the AF-ON button on the back and keep it pressed (again using AF one-shot) then the half-press of the shutter only sets exposure (for this both AF-ON is pressed and the shutter is half-pressed). So I don't really understand why decoupling AF from the shutter might be useful. Maybe if you use the other AF modes, AI Focus and AI Servo, then it might be important. I have found these not to be very useful, myself.

I am used to going full manual (both focus and exposure) because some of the landscape photos I take require that to turn out correctly (panoramas and very long exposures, for instance), and back in the pre-AF days it was of course the only way.

Bramble9 · Nov 10, 2015

Nope. I don't have multiple accounts and am not John Lock 2015.

edit: I see what you mean. Every once in a while I clear my browser and dpreview seems to automatically re-set my name to John Lock 2015-- don't know why? But in any event, I just want access to the forum for questions and answers such as in this thread. Still, I'll try to clear it up though I'm not that computer literate.

JL

Re 70D and back button AF?

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