cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 

Back-button focus

Last week I had an "optional" photo shoot at a civic event in our town, so I used the opportunity to experiment with back-button focus. I'd never used it, but a friend who's a sports photographer had told me how much he liked it (each of us has a 5D Mark III), so I set up the buttons and gave it a try.

 

Overall, BBF worked pretty much as I had expected; and while I didn't really notice any significant benefit for the kind of photography I do (landscapes, architecture, and events, mostly), I could see where it could be useful in certain circumstances. But one thing bothered me: When I edited the pictures in DPP 4, there were no red squares to indicate which AF points had achieved focus. (I was using the mode that divides the AF points into groups; and if any point in the selected group achieves focus, that's what's used.) I guess I can see the logic to it. With BBF it's assumed that that there's a high probability that you'll recompose, in which case a red square wouldn't necessarily mean that what's behind it is what was in focus. But I found it a bit annoying anyway. After all, you can recompose with shutter-button focus, and that doesn't make the red squares go dark. Is that really how it works, or am I missing something?

Bob
Philadelphia, Pennsylvania USA
19 REPLIES 19

No, cannot see the point of that. If you use back button for focus then in AI Servo just take your thumb off it and it stops, assuming of course you have also removed the focus operation from the shutter button.


@Ray-uk wrote:

No, cannot see the point of that. If you use back button for focus then in AI Servo just take your thumb off it and it stops, assuming of course you have also removed the focus operation from the shutter button.


If you use BBF you have to keep pressing the back button for continuous focus.

 

So if you are shooting a sequence of action shots (moving subject) you have to press both the shutter and the back button at the same time.

 

As a sports and wildlife photographer I want continuous focus most of the time. I only want to stop focus on rare occasions. So I'm going to have to press two buttons most of the time, so on rare occasions I can remove my thumb and stop focus? Seems silly to me. Why would you want to have to press two buttons most of the time?

 


@TTMartin wrote:

If you use BBF you have to keep pressing the back button for continuous focus.

 

So if you are shooting a sequence of action shots (moving subject) you have to press both the shutter and the back button at the same time.

 

As a sports and wildlife photographer I want continuous focus most of the time. I only want to stop focus on rare occasions. So I'm going to have to press two buttons most of the time, so on rare occasions I can remove my thumb and stop focus? Seems silly to me. Why would you want to have to press two buttons most of the time?

 


Yes, I see your point, as I don't do much action stuff I haven't had that problem but it is well worth considering.


@TTMartin wrote:

@Ray-uk wrote:

No, cannot see the point of that. If you use back button for focus then in AI Servo just take your thumb off it and it stops, assuming of course you have also removed the focus operation from the shutter button.


If you use BBF you have to keep pressing the back button for continuous focus.

 

So if you are shooting a sequence of action shots (moving subject) you have to press both the shutter and the back button at the same time.

 

As a sports and wildlife photographer I want continuous focus most of the time. I only want to stop focus on rare occasions. So I'm going to have to press two buttons most of the time, so on rare occasions I can remove my thumb and stop focus? Seems silly to me. Why would you want to have to press two buttons most of the time?

 


TTMartin, I'm not sure I'm following you very well...I may learn something new after this... 🙂

 

The way I shoot birds is that I track and focus lock on the bird by AI Servo which means the focus button is continuously pressed.  When I feel I got perfect everything, I press the shutter to take the shot.  In the default, as you know, I'd have to half press the Shutter button to AI focus then fully press to take a picture.  The primary reason I use BBF was that I don't want to inadvertently press the shutter button while doing continous focus (AI Servo) by traditionally half-pressing the shutter button.  I tend to get overexcited and press the shutter a little too hard while I'm not ready.  When I have only a second or two to shoot after waiting for hours, a mis-timed shutter trip can be disastrous when focus has not yet been achieved.  It happened to me more than once and that was why I switched to BBF.  I only press the shutter to take the shot and I don't need to press the focus button while taking the shots so I never press two buttons at the same time anyhow and if I did, it wouldn't matter.

 

Another problem with the regular shutter focusing scheme is it refocuses on you when you press the shutter to take a shot.  I hate that in some cases.  By using the BBF, I don't have to deal with this.

 

 

================================================
Diverhank's photos on Flickr


@diverhank wrote:

@TTMartin wrote:

@Ray-uk wrote:

No, cannot see the point of that. If you use back button for focus then in AI Servo just take your thumb off it and it stops, assuming of course you have also removed the focus operation from the shutter button.


If you use BBF you have to keep pressing the back button for continuous focus.

 

So if you are shooting a sequence of action shots (moving subject) you have to press both the shutter and the back button at the same time.

 

As a sports and wildlife photographer I want continuous focus most of the time. I only want to stop focus on rare occasions. So I'm going to have to press two buttons most of the time, so on rare occasions I can remove my thumb and stop focus? Seems silly to me. Why would you want to have to press two buttons most of the time?

 


TTMartin, I'm not sure I'm following you very well...I may learn something new after this... 🙂

 

The way I shoot birds is that I track and focus lock on the bird by AI Servo which means the focus button is continuously pressed.  When I feel I got perfect everything, I press the shutter to take the shot.  In the default, as you know, I'd have to half press the Shutter button to AI focus then fully press to take a picture.  The primary reason I use BBF was that I don't want to inadvertently press the shutter button while doing continous focus (AI Servo) by traditionally half-pressing the shutter button.  I tend to get overexcited and press the shutter a little too hard while I'm not ready.  When I have only a second or two to shoot after waiting for hours, a mis-timed shutter trip can be disastrous when focus has not yet been achieved.  It happened to me more than once and that was why I switched to BBF.  I only press the shutter to take the shot and I don't need to press the focus button while taking the shots so I never press two buttons at the same time anyhow and if I did, it wouldn't matter.

 

Another problem with the regular shutter focusing scheme is it refocuses on you when you press the shutter to take a shot.  I hate that in some cases.  By using the BBF, I don't have to deal with this.

 

 


As far as inadvertantly taking a shot when you haven't achieved focus, that is a parameter you can set in the camera. If you set it right it won't take a photo without achieving focus in AIServo, just like wont in One Shot.

 

How to do you focus on birds flying towards you if you aren't pressing both the back button and the shutter button?

 

16586885_10158181984085693_1517571621069334547_o.jpg

 

 

A00A8938.jpg

 

Those two are the last of about a sequence of 6.

As Art Morris says, 'when something happens press the shutter button'. I'd rather be able to do that then have to do a two button sequence. 

 

By setting up the AF ON button to AF OFF you don't have to deal with the camera refocusing when you don't want it to as you can simply press the back AF 'OFF' button to stop it from refocusing. Times when I don't want continuous AF like focusing on a bird sitting on a branch through other branches of a tree, those then to be more laid back occurrences. I have the extra time to focus on the bird, either manual focus or slight focus and recompose, while pushing the back AF 'OFF' button.

 

FWIW, if you switched to AF OFF for action photography after learning about the AF OFF option you wouldn't be the first. I know of a couple of dedicated BBF users, who switched after learning about AF OFF.

 

BBF is actually very old tech going back to EOS film cameras (using the * ), AF OFF is something relatively new that only became available when Canon added the dedicated AF ON button. By providing a dedicated AF ON button for BBF they effectively outdated BBF, because with the AF ON button came option of reprogramming it to AF OFF.

 

 

Another example of tracking a bird moving towards the camera.

Glossy Ibis photobomb (near midair collision)*.


*All images in the GIF are copyright Tom V. Martin (All Rights Reserved)

"No, cannot see the point of that."

 

......and here comes a MTF chart to prove it. Smiley LOL

EB
EOS 1DX and 1D Mk IV and several lenses!

diverhank
Authority

@RobertTheFat wrote:

When I edited the pictures in DPP 4, there were no red squares to indicate which AF points had achieved focus. (I was using the mode that divides the AF points into groups; and if any point in the selected group achieves focus, that's what's used.) 


This is interesting...I've been using BBF for years now.  I had never paid any attention to the red squares and how they work but I can tell you recently I was doing a presentation on photography and needed a couple of pictures showing the red square focus and I used DPP and got the squares.  

 

Granted I only grabbed a couple of pictures to do that and got the squares.  I don't doubt depending on the settings, sometimes you don't get the squares.  So at least for me, the squares are still there, using BBF.  For these pictures, I did not recompose, if that's making any difference.

================================================
Diverhank's photos on Flickr


@diverhank wrote:

@RobertTheFat wrote:

When I edited the pictures in DPP 4, there were no red squares to indicate which AF points had achieved focus. (I was using the mode that divides the AF points into groups; and if any point in the selected group achieves focus, that's what's used.) 


This is interesting...I've been using BBF for years now.  I had never paid any attention to the red squares and how they work but I can tell you recently I was doing a presentation on photography and needed a couple of pictures showing the red square focus and I used DPP and got the squares.  

 

Granted I only grabbed a couple of pictures to do that and got the squares.  I don't doubt depending on the settings, sometimes you don't get the squares.  So at least for me, the squares are still there, using BBF.  For these pictures, I did not recompose, if that's making any difference.


Well, if not recomposing means that you didn't take your thumb off the button, I guess that's consistent with what Waddizzle said earlier. The camera abandons the red squares if you release the button because it assumes you've recomposed.

 

So one important difference between BBF and shutter-button focus, at least in one-shot mode, is that with BBF it can tell that you may have recomposed, while with SBF it can't. Does that make sense?

Bob
Philadelphia, Pennsylvania USA


@RobertTheFat wrote:

@diverhank wrote:

@RobertTheFat wrote:

When I edited the pictures in DPP 4, there were no red squares to indicate which AF points had achieved focus. (I was using the mode that divides the AF points into groups; and if any point in the selected group achieves focus, that's what's used.) 


 


Well, if not recomposing means that you didn't take your thumb off the button, I guess that's consistent with what Waddizzle said earlier. The camera abandons the red squares if you release the button because it assumes you've recomposed.

 

So one important difference between BBF and shutter-button focus, at least in one-shot mode, is that with BBF it can tell that you may have recomposed, while with SBF it can't. Does that make sense?


Yes, I think I understand what you puzzling out.  Maybe this helps.  While DPP doesn't display the AF points if you're not pressing the BBF button, the data is still recorded.  DPP just doesn't show it to you.  This is what the LR Plug-in shows you.

 

LR_FocusInfo_01.JPG

 

Here's a closeup of the Legend.

 

LR_FocusInfo_02.JPG

 

The top state occurs when you lock focus in One Shot with BBF, and then recompose with your thumb off the button.  The first state also occurs when you use AI Servo and lock on a subject.

The second state is what occurs when you hod the button when you activate the shutter.  The third state is pretty much self-explanatory.  The fourth state occurs when you never press BBF.

--------------------------------------------------------
"The right mouse button is your friend."
Announcements
11/22/2022: New firmware available for EOS R3, EOS R7 and EOS R10
11/16/2022: We're thrilled to be ranked among the Best Employers for Veterans in 2022 by Forbes.
10/14/2022: Help ensure your autofocus is properly aligned with a Canon Precision Alignment
09/19/2022: New firmware version 1.0.4.1 is available for EOS C70
08/31/2022: New firmware version 1.1.1 is available for RF 70-200mm L IS USM
08/09/2022: New firmware version 1.2.0 is available for CR-N 300
08/09/2022: New firmware version 1.2.0 is available for CR-N 500
07/28/2022: New firmware version 1.2.1 is available for EOS-R3
07/21/2022: New firmware version 1.6.0 is available for EOS-R5
07/21/2022: New firmware version 1.6.0 is available for EOS-R6
07/21/2022: New firmware version 1.1.0 is available for EOS-R7
07/21/2022: New firmware version 1.1.0 is available for EOS-R10
07/14/2022: New firmware version 1.0.1 is available for CR-X300
07/01/2022: New firmware version 1.3.0 is available for PowerShot PICK
06/10/2022: Service Notice:UPDATE: Canon Inkjet Printer continuous reboot loop or powering down
06/07/2022: New firmware version 1.3.2 is available for PowerShot G7 X Mark III
06/07/2022: New firmware version 1.0.3 is available for EOS M50 Mark II
05/31/2022: Did someone SAY Badges?
05/26/2022: New firmware version 1.0.5.1 is available for EOS-C500 Mark II
05/26/2022: New firmware version 1.0.3.1 is available for EOS-C300 Mark III
05/10/2022: Keep your Canon gear in optimal condition with a Canon Maintenance Service
05/05/2022: We are excited to announce that we have refreshed the ranking scale within the community!
04/26/2022: New firmware version 1.0.1.1 is available for EOS R5 C
03/23/2022: New firmware version 1.0.3.1 is available for EOS-C70
02/09/2022: Share Your Photos is back!
02/07/2022: New firmware version 1.6.1 is available for EOS-1DX Mark III
01/19/2022: READY FOR ANYTHING EOS-R5 C
01/13/2022: Community Update. We will be retiring the legacy profile avatars on 01/20/2022. Click this link to read more.
01/05/2022: Welcome to CES 2022!