7D Back button focus?

Started Dec 27, 2012 | Questions
Wei Kelun
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7D Back button focus?
Dec 27, 2012

What are the advantages of using the back button to focus on the 7D? When people talk about "back button focussing", does that just mean that the AF-ON button is set via C.FnIV.1 to "Metering and AF start"? If so, then it seems to do exactly what pressing the shutter half-way does, so I don't see the point of using the button in the back... So I'm probably missing something.

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Canon EOS 7D
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garyknrd
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Re: Back button focus?
In reply to Wei Kelun, Dec 27, 2012

I use it now. For the past year. Not sure it helps that much. I am a birder, using AF-servo mode I use it to AF on the bird when I like the shot then I press the shutter button. There is a lot of hype about it. Kinda over rated I think. But now that I am used to it I will not go back. You can program all the buttons to do different things. I use the big button on the back of the 7D. Some use the small button on the Lt.

Not much help but my point of view.

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Sonoran Sam
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Re: 7D Back button focus?
In reply to Wei Kelun, Dec 27, 2012

I use it all the time for birding, as a lot of times the object I'm shooting gets behind branches, trunks, etc. so all I have to do is release the back button focus and follow till it clears up. Another this is I will focus on a spot and wait for the bird to get to that area and maybe a branch is there so when I press the shutter release it will not refocus and I will miss a shot.  Once you get used to it, you will find you really like it.  Focus once press shutter many times.

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Wei Kelun
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Re: 7D Back button focus?
In reply to Wei Kelun, Dec 27, 2012

All right, so I think I'm beginning to understand. You guys are disabling the shutter-half-way option, so that pressing the shutter half-way doesn't focus, but just meters?

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elfroggio
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Re: 7D Back button focus?
In reply to Wei Kelun, Dec 28, 2012

Wei Kelun wrote:

What are the advantages of using the back button to focus on the 7D? When people talk about "back button focussing", does that just mean that the AF-ON button is set via C.FnIV.1 to "Metering and AF start"? If so, then it seems to do exactly what pressing the shutter half-way does, so I don't see the point of using the button in the back... So I'm probably missing something.

It took me a few month to get used to the back button focus (but I'm a old dinosaur, aka a klutz). Now, I wouldn't have it any other way.

The main point of using the back button focus (BBF) vs the half press of the shutter is that with the BBF, I control when I want the camera to focus. With the focus as part of the half press, the camera will refocus when pressing on the shutter, which may or may not be what I want. Too often, it's not what I want.

I decide when to focus and not the camera.

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happysnapper64
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Re: 7D Back button focus?
In reply to Wei Kelun, Dec 28, 2012

Wei Kelun wrote:

All right, so I think I'm beginning to understand. You guys are disabling the shutter-half-way option, so that pressing the shutter half-way doesn't focus, but just meters?

Wei Kelun. I have been meaning to ask this question for a while. You seem to have come to the same conclusion I have in this post, so I will watch out for replies.

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lee uk.
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Wei Kelun
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Re: 7D Back button focus?
In reply to happysnapper64, Dec 28, 2012

happysnapper64 wrote:

Wei Kelun wrote:

All right, so I think I'm beginning to understand. You guys are disabling the shutter-half-way option, so that pressing the shutter half-way doesn't focus, but just meters?

Wei Kelun. I have been meaning to ask this question for a while. You seem to have come to the same conclusion I have in this post, so I will watch out for replies.

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lee uk.
There are old pilots, & there are bold pilots, but there are no old bold pilots.

For the last hour, I've been playing with this. I used C.F.IV.1 to set the AF-ON button to "Metering and AF start" and the shutter button half-press to "Metering start" only. I think this is what everyone's talking about. (Experts, please jump in here.)

Pro's are that it's much easier to focus and recompose, because you don't have to keep the shutter button half-way pressed, and in fact, you don't need to keep any buttons pressed at all. Just hold AF-ON until it achieves focus, and then let go and compose your shot. Another pro is that you can take a picture at any time by pressing the shutter button all the way, no need to wait for autofocus. This could be important someday.

Cons: Two that I can think of. First, it makes the post-exposure indication of the AF point meaningless, since there's no indication whether the shot was recomposed after focussing. This can be mitigated somewhat, in that the selected AF points only show up on the LCD back when you take the picture while holding AF-ON, meaning you're working both buttons when you take the shot. That keeps you from forgetting what you're doing. Still, the post-exposure display loses some meaning with regard to the AF points used for the photo unless you're disciplined about always using both buttons together.

Second con: it makes handing your camera to a friend more complicated, since they won't immediately get the concept.

That being said, I think I like it. After an hour, it's become intuitive, and I really like how easy it makes recomposing a shot without needing to sit on the shutter button.

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AveshV
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Re: 7D Back button focus?
In reply to Wei Kelun, Dec 28, 2012

I set the back button to focus as you've done, and the shutter half press to AE Lock, and set metering to Spot which gives me full control of the shot.

Try it you might like it

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KeBul
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Re: 7D Back button focus?
In reply to Wei Kelun, Dec 28, 2012

As Suave says, set the shutter half press to AE lock, and with AF on the * button and AF set to servo to have the best of all worlds... metering mode can be a personal choice, I prefer centre weighted partial myself...

As you've found out...

For focus you can single focus on the * button, aim-press *-focus-release star and then recompose if required, you adjust focus with another press of the * button, or track by press and hold if you are in servo mode.

and then similarly for metering you can frame for metering, press and half hold shutter to lock that exposure, then recompose for the final shot, or wait on the half press until after you've composed and then meter the shot at that stage if lighting allows.

Been using this setup for many years now and have rarely switched back to normal, I find if I pick up someone elses camera I thumb the * button and wonder why it doesn't focus, explaining to those that are going to use mine to press the * with their thumb to focus hasn't been too much trouble over the years and a couple of friends I've shown this setup to have moved to it permanently as well.

Disadvantages for me are I sometimes get "thumb lock" and keep holding the * button down on a static subject, so the focus hunts a little bit giving me slight focus variation from shot to shot and there are reports that one shot is more reliable on MkIV's and I have seen mine struggle to lock any sort of focus under certain circumstances when using this setup but haven't had the presence of mind to swap to one shot to see if it resolves the issue.

Kev

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Wei Kelun
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Re: 7D Back button focus?
In reply to KeBul, Dec 28, 2012

Any reason you're putting AF on the " * " button instead of on the AF-ON button? The latter seems a bit easier to find, since it's at the end of the row all by itself.

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Alastair Norcross
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Re: 7D Back button focus?
In reply to Wei Kelun, Dec 28, 2012

Wei Kelun wrote:

Any reason you're putting AF on the " * " button instead of on the AF-ON button? The latter seems a bit easier to find, since it's at the end of the row all by itself.

I use both. AF-ON for the main focus point, and the " * " button for the alternate focus point. One great feature of the 7D is that you can set up an alternate focus point too. Additionally, if your main point isn't the center point, you can switch back and forth between that and the center point by pressing the center of the joystick. This way, you can have three different focus points easily and quickly accessible. Add to that the feature to use different focus points in horizontal and vertical orientations, and you have a very flexible focusing system.

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Keith Z Leonard
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Re: 7D Back button focus?
In reply to Wei Kelun, Dec 28, 2012

Wei Kelun wrote:

For the last hour, I've been playing with this. I used C.F.IV.1 to set the AF-ON button to "Metering and AF start" and the shutter button half-press to "Metering start" only. I think this is what everyone's talking about. (Experts, please jump in here.)

Pro's are that it's much easier to focus and recompose, because you don't have to keep the shutter button half-way pressed, and in fact, you don't need to keep any buttons pressed at all. Just hold AF-ON until it achieves focus, and then let go and compose your shot. Another pro is that you can take a picture at any time by pressing the shutter button all the way, no need to wait for autofocus. This could be important someday.

I don't use focus/recompose often with the 7D, the 19 points are all cross type and sufficient to cover most of my needs.  Recomposing shifts the plane of focus and can cause OOF shots.

Cons: Two that I can think of. First, it makes the post-exposure indication of the AF point meaningless, since there's no indication whether the shot was recomposed after focussing. This can be mitigated somewhat, in that the selected AF points only show up on the LCD back when you take the picture while holding AF-ON, meaning you're working both buttons when you take the shot. That keeps you from forgetting what you're doing. Still, the post-exposure display loses some meaning with regard to the AF points used for the photo unless you're disciplined about always using both buttons together.

post-exposure indication here has nothing to do with what button you used to AF, you are talking about the fact that it's pointless if you focus and recompose, which is not a great practice anyway if you have all high quality AF points, quite frankly.

Second con: it makes handing your camera to a friend more complicated, since they won't immediately get the concept.

This is certainly true, though I've found that most people are used to contrast AF now a days and don't get the whole focus point thing anyway.  I did manage to get my brother trained up for center point only PDAF, so he takes the shots that I need to be in.  

The biggest advantage I found for separating the AF and shutter release is for situations where the focus doesn't need to change for a series of shots, you AF once, then just shoot.  This means I don't have to hit the 'MF' switch on the lens.  There are a lot of instances where this is the case, sometimes you want to take a shot when a certain point in space is reached, sometimes the lighting isn't great and AF can be slow, so you don't want to AF repeatedly for the same result, that sort of thing.

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Mark Salvetti
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Re: 7D Back button focus?
In reply to Wei Kelun, Dec 28, 2012

Wei Kelun wrote:

Cons: Two that I can think of. First, it makes the post-exposure indication of the AF point meaningless, since there's no indication whether the shot was recomposed after focussing. This can be mitigated somewhat, in that the selected AF points only show up on the LCD back when you take the picture while holding AF-ON, meaning you're working both buttons when you take the shot. That keeps you from forgetting what you're doing. Still, the post-exposure display loses some meaning with regard to the AF points used for the photo unless you're disciplined about always using both buttons together.

That first con is actually a moot point - if you focus and recompose using the back button, you are not holding down the back button when you take the shot.  That means no focus points will show up post-exposure.

When you move AF to a back button, the focus points will only show up post-exposure if you are holding down the back button when the exposure is taken.

Mark

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Peter too
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Re: 7D Back button focus?
In reply to Keith Z Leonard, Dec 28, 2012

Keith Z Leonard wrote:

The biggest advantage I found for separating the AF and shutter release is for situations where the focus doesn't need to change for a series of shots, you AF once, then just shoot. This means I don't have to hit the 'MF' switch on the lens. There are a lot of instances where this is the case, sometimes you want to take a shot when a certain point in space is reached, sometimes the lighting isn't great and AF can be slow, so you don't want to AF repeatedly for the same result, that sort of thing.

One situation I had was when I tried to photograph a blue tit against a blue sky shortly after leaving a bird box. I knew which way the bird tended to fly, I didn't want the shot to be with the bird box in the background and there was no time to refocus after the bird left the box. So I focussed on the box, recomposed into the space against the sky, waited for the bird to poke its head out of the box and then ran the shutter until the bird had gone.

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Keith Z Leonard
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Re: 7D Back button focus?
In reply to Peter too, Dec 28, 2012

Good point, I do that occasionally with humming birds near the feeder, they tend to duck in and out of the feeder, so you can set your focus, shoot with enough DOF and fire away.

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skycam1225
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Re: 7D Back button focus?
In reply to Keith Z Leonard, Dec 29, 2012

I use the same technique as Keith!

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checkmate91
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Re: 7D Back button focus?
In reply to Wei Kelun, Dec 30, 2012

Wei Kelun wrote:

Second con: it makes handing your camera to a friend more complicated, since they won't immediately get the concept.

That being said, I think I like it. After an hour, it's become intuitive, and I really like how easy it makes recomposing a shot without needing to sit on the shutter button.

Regarding the second con, whenever I have handed my camera over to a friend or colleague the conversation usually goes something like this:

Me: the AF is on the back and the exposure is half shutter button.

Them: Eh, what?

Me: I said turn the knob on the left round to the green square and start shooting.

I too like the flexibility of focussing on the subject and recomposing/ adjusting exposure.

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janecee7
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Re: 7D Back button focus?
In reply to elfroggio, Dec 30, 2012

One thing that hasn't been pointed out as an advantage of BBF is the ability to quickly switch to manual focus without changing the button on the lens to MF.  You simply focus manually, then release the shutter.  If you try to do this without BBF, the camera will refocus when you depress the shutter.   I found this to be quite helpful when using manual focus/live view on my tripod for landscape shots, but still having the ability to quickly do autofocus if I choose.

I don't know for sure that you can do this with all lenses, but it works with the five that I use most.

Jane

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GPapa
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Good Observation.
In reply to janecee7, Dec 30, 2012

I have been doing that without realizing it was a feature made available by using a back focus button.

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Keith Z Leonard
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Re: 7D Back button focus?
In reply to janecee7, Dec 30, 2012

For lenses that have full time MF, some don't...you do that too much and you need a new lens.

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