Back Button Focusing...
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Dec 24, 2020 09:47:45 #
I have been reading some what on B.B.F.
I'm kind of confused as to whether it is something to use for bird in flight photo's.
Kind help on this would be appreciated.
Tom
I'm kind of confused as to whether it is something to use for bird in flight photo's.
Kind help on this would be appreciated.
Tom
Dec 25, 2020 08:16:01 #
jbk224
Loc: Long Island, NY
Tom, check out Steve Perry's video and blog on BBF. I think you will become a convert..and if not, certainly have a great resource.
https://backcountrygallery.com/af-on-and-back-button-autofocus/
https://backcountrygallery.com/af-on-and-back-button-autofocus/
Dec 28, 2020 14:00:30 #
amfoto1
Loc: San Jose, Calif. USA
The biggest single advantage of using BBF is that it allows you to leave the camera in continuous focus all the time.
Continuous focus AF is called different names by various manufacturers. In Canon it's "AI Servo" or "Servo AF", depending upon the camera. In Nikon it's called "AFC". Basically, continuous focus is for moving subjects. It simply keeps updating the focus as long as you press the button. It also can be used with stationary subjects, but if not using BBF can be a problem with certain techniques.
Non-continuous focus AF is also called different things depending upon the manufacturer. Canon's is "One Shot" and Nikon's is "AFS" or "Single Shot". In this mode once focus is achieved the AF system stops and "locks". If a subject moves, or the photographer moves and distances change, focus isn't maintained the way it is with continuous focus. With non-continuous focus you have to consciously re-focus any time the distance to subject changes for any reason. That means lifting off the button, then re-applying pressure to cause the lens and camera to reacquire focus. It's easy to forget to do this and end up missing focus. It's even worse with moving subjects. Unless they're moving very, very slowly or moving directly parallel to you and maintaining the same distance, the subject will end up out of focus by the time you press the shutter release! (At sporting events I shoot, I hear peoples' cameras "beeping" focus confirmation all the time, which tells me they are in the wrong focus mode for moving subjects and they will miss focus more often than not.)
Both continuous focus and non-continuous focus work fine, for different types of subjects. However a problem is having to pause to change focus mode when a subject starts or stops moving, or if the photographer switches back and forth between shooting moving and stationary subjects. It's worse with cameras where you have to go into a menu or press multiple buttons and/or spin a dial to make the change. Some cameras allow you to map the changes to a button so it can be done with a single press. But even then you may miss some shots while switching modes. Wouldn't it be better to not even have to think about it? That's largely possible by using BBF.
BBF essentially lets you leave your camera in continuous AF mode all the time and be ready for anything, with some minor exceptions.
BBF puts you in control of when AF works and allows you to start and stop it with your thumb.
When the AF is still tied to the shutter release button "focus and recompose" technique with stationary subjects or similar "pre-focus" technique with moving subjects are both impossible while using continuous AF. As soon as you move the AF point off the subject to reframe the image or off of where you wanted to pre-focus, the AF will want cause camera and lens to re-focus elsewhere. But if you instead set up BBF, you can do both these techniques easily. Once focus is achieved, lift off that back button so that AF stops and won't change, leaving you free to go ahead and reframe as you see fit.
There are some other advantages of using continuous AF all the time. For example, many modern zoom lenses are "varifocal" designs. This means they don't maintain focus when zoomed. That can be a problem when not using continuous AF. You have to consciously cause the camera and lens to re-focus by lifting off the button, then re-applying pressure on it. With a varifocal zoom you have to do this every time you change the focal length! However, if you're instead using continuous AF it will automatically and instantly correct for the loss of focus when the varifocal lens is zoomed. And BBF makes it possible to use continuous focus as your default mode.
One minor issue using continuous AF is there may be limited or no "focus confirmation". It varies by camera and system, but most will "beep" or flash an LED or something when focus is achieved in non-continuous focus mode. But those notifications may not occur at all while using continuous focus. You have to learn to "see and feel" focus acquisition without these assists. With a little practice you can learn how long it takes to achieve focus (varies by camera and lens) and may be able to see it in the viewfinder (easier with larger, brighter viewfinders). This isn't directly tied to BBF, but is a consideration with continuous focus that BBF enables. If focus is really critical and time allows, even still using BBF you can switch back to non-continuous focus and in many cameras even magnify the image preview in Live View to more closely check that focus is precisely where you want it.
Give BBF a try. Most people get accustomed to it within a few days, many really like it and it can be used in almost any shooting situation with nearly all types of subjects. BBF certainly is not just for birds in flight. It can be used for practically anything. It's definitely useful for moving subjects, but works great even for stationary ones. Mainly it lets you leave the camera in one mode and that saves having to pause to change your camera and lens settings, potentially missing shots.
I switched to using BBF some 20 years ago and think it really helps my percentage of in-focus shots. I shoot a lot of sports and action, so it's ideal for me and I very rarely switch out of BBF (mostly just if I lend a camera to someone who doesn't know how to use it). BBF puts me in more full control of when and where the camera and lens focus.
Besides, you have nothing to lose. If you don't like BBF for any reason, you can always switch back.
Continuous focus AF is called different names by various manufacturers. In Canon it's "AI Servo" or "Servo AF", depending upon the camera. In Nikon it's called "AFC". Basically, continuous focus is for moving subjects. It simply keeps updating the focus as long as you press the button. It also can be used with stationary subjects, but if not using BBF can be a problem with certain techniques.
Non-continuous focus AF is also called different things depending upon the manufacturer. Canon's is "One Shot" and Nikon's is "AFS" or "Single Shot". In this mode once focus is achieved the AF system stops and "locks". If a subject moves, or the photographer moves and distances change, focus isn't maintained the way it is with continuous focus. With non-continuous focus you have to consciously re-focus any time the distance to subject changes for any reason. That means lifting off the button, then re-applying pressure to cause the lens and camera to reacquire focus. It's easy to forget to do this and end up missing focus. It's even worse with moving subjects. Unless they're moving very, very slowly or moving directly parallel to you and maintaining the same distance, the subject will end up out of focus by the time you press the shutter release! (At sporting events I shoot, I hear peoples' cameras "beeping" focus confirmation all the time, which tells me they are in the wrong focus mode for moving subjects and they will miss focus more often than not.)
Both continuous focus and non-continuous focus work fine, for different types of subjects. However a problem is having to pause to change focus mode when a subject starts or stops moving, or if the photographer switches back and forth between shooting moving and stationary subjects. It's worse with cameras where you have to go into a menu or press multiple buttons and/or spin a dial to make the change. Some cameras allow you to map the changes to a button so it can be done with a single press. But even then you may miss some shots while switching modes. Wouldn't it be better to not even have to think about it? That's largely possible by using BBF.
BBF essentially lets you leave your camera in continuous AF mode all the time and be ready for anything, with some minor exceptions.
BBF puts you in control of when AF works and allows you to start and stop it with your thumb.
When the AF is still tied to the shutter release button "focus and recompose" technique with stationary subjects or similar "pre-focus" technique with moving subjects are both impossible while using continuous AF. As soon as you move the AF point off the subject to reframe the image or off of where you wanted to pre-focus, the AF will want cause camera and lens to re-focus elsewhere. But if you instead set up BBF, you can do both these techniques easily. Once focus is achieved, lift off that back button so that AF stops and won't change, leaving you free to go ahead and reframe as you see fit.
There are some other advantages of using continuous AF all the time. For example, many modern zoom lenses are "varifocal" designs. This means they don't maintain focus when zoomed. That can be a problem when not using continuous AF. You have to consciously cause the camera and lens to re-focus by lifting off the button, then re-applying pressure on it. With a varifocal zoom you have to do this every time you change the focal length! However, if you're instead using continuous AF it will automatically and instantly correct for the loss of focus when the varifocal lens is zoomed. And BBF makes it possible to use continuous focus as your default mode.
One minor issue using continuous AF is there may be limited or no "focus confirmation". It varies by camera and system, but most will "beep" or flash an LED or something when focus is achieved in non-continuous focus mode. But those notifications may not occur at all while using continuous focus. You have to learn to "see and feel" focus acquisition without these assists. With a little practice you can learn how long it takes to achieve focus (varies by camera and lens) and may be able to see it in the viewfinder (easier with larger, brighter viewfinders). This isn't directly tied to BBF, but is a consideration with continuous focus that BBF enables. If focus is really critical and time allows, even still using BBF you can switch back to non-continuous focus and in many cameras even magnify the image preview in Live View to more closely check that focus is precisely where you want it.
Give BBF a try. Most people get accustomed to it within a few days, many really like it and it can be used in almost any shooting situation with nearly all types of subjects. BBF certainly is not just for birds in flight. It can be used for practically anything. It's definitely useful for moving subjects, but works great even for stationary ones. Mainly it lets you leave the camera in one mode and that saves having to pause to change your camera and lens settings, potentially missing shots.
I switched to using BBF some 20 years ago and think it really helps my percentage of in-focus shots. I shoot a lot of sports and action, so it's ideal for me and I very rarely switch out of BBF (mostly just if I lend a camera to someone who doesn't know how to use it). BBF puts me in more full control of when and where the camera and lens focus.
Besides, you have nothing to lose. If you don't like BBF for any reason, you can always switch back.
Dec 28, 2020 18:13:00 #
Wow amfoto,
Thanks for that great explaination of BBF.
I've started to do more birds in flight lately and I have seen where a lot of bird photographers speak of using BBF for that.
I also do a lot of horse shows, it seems like this woulsd be put to good use for that also.
I shall have to give it a try and see how it works for me. I well have to try on birds for now and see how it goes, the horse shows dont start back up until March,
plenty of time to practice...
Thanks so much for your reply,
Tom
Thanks for that great explaination of BBF.
I've started to do more birds in flight lately and I have seen where a lot of bird photographers speak of using BBF for that.
I also do a lot of horse shows, it seems like this woulsd be put to good use for that also.
I shall have to give it a try and see how it works for me. I well have to try on birds for now and see how it goes, the horse shows dont start back up until March,
plenty of time to practice...
Thanks so much for your reply,
Tom
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