03-03-2014 11:09 PM
I cannot get my 6D's back button focus (AF-ON) to work. After following directions on Canon's website on how to set it up, the button just does not do anything. Auto focus only works with the shutter button. I have the function set to "P" which I understood to be o.k. Would resetting the camera to factory default help? I would prefer not to have to send the camera to Canon for a one button repair. The camera body was purchased new and is still under warranty.
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03-03-2014 11:34 PM - edited 03-03-2014 11:49 PM
It's super easy to set up BBF on a 6D....
If you have already been changing some things and are unsure which ones, you might want to reset all the Custom Functions to factory default, before starting. (Note: There is a way to view which C.Fns are set and to what each is assigned... As you enter each of the four C.Fn groups, note the list in the lower LH corner of the LCD screen, that shows all the C.Fns in that group at a glance. The top line is the C.Fn number, the bottom line is the setting for each C.Fn.)
To set up BBF....
All you have to do is go into the menu, Custom Functions, C.Fn III-5, operations/others, button assignments. Select and enter that and then press "set" and this should take you right to the top of the LH column, which is a graphic illustration of the shutter release button. Press set again to enter this, then scroll to select the center option "start metering" and press "set" once more to select this choice, then press "menu" button several times to back out of the menus. Done!
What this does is remove AF start from the shutter release button. By default it's already assigned to the AF-On button on the back of the camera too, so BBF is set up and ready to use as soon as you remove it from the shutter release button.
Metering and Image Stabilization will continue to start with a half press of the shutter release button or whenever you press the AF-On button. But AF will only start with your thumb on the AF-On button. Using BBF, you now can use AI Servo most of the time, for stationary or moving subjects. If you want to "focus and recompose", simply focus and then lift your thumb off the AF-On button to leave focus where it is and recompose as you see fit. (Without BBF, you cannot do focus and recompose.... it will cause mis-focused shots.) You still might want to switch back to One Shot when you want high precision focus with stationary subjects.
There is another option you may want to consider...
Using the same Custom Function III-5, if you prefer you can swap the functions of the AF-On and * (AE Lock) buttons. I do this on my cameras for a couple reasons: One is that the * button is larger, more prominent, and closer to my thumb... so I prefer to use it for focusing. The other reason is that older Canon models that didn't have the AF-On button, you had to use the * button and that's the way I learned to use BBF (Note: In some cases there was an AF-On button on the body but not on the vertical grip, while older cameras simply didn't have an AF-On button at all, on the body or the grip).
03-04-2014 11:08 AM
Alan, finally got it to work. I also took your suggestion and set it to AI Servo. Not fully understanding all the AI Servo choices, I set it to the middle setting.
It's good to know the button works!!!
Thanks so much
03-04-2014 01:36 PM
Glad to hear you got BBF set up. It takes a little practice, but soon becomes second nature to focus that way.
I am not sure what you mean by "AI Servo choices".
Are you new to Canon cameras and their focusing systems? Just in case you are...
Like most Canon cameras, the 6D has three auto focus modes: One Shot, AI Focus and AI Servo.
One Shot is for use with stationary subjects. The focus is performed, then stops and locks, and Focus Confirmation is given (the green LED in the viewfinder, red flash of the AF point in the viewfinder, and if it's enabled, the "beep"). If anything moves, you or the subject, or if you change the focal length of most zooms, to re-focus you have to lift pressure completely off the focus buttion (whether it's BBF or half press of the shutter release), then reapply it.
One time this is quite important to remember is when using a zoom, since most modern ones are "varifocal" designs that don't maintain focus when the focal length is changed by zooming. If using One Shot and a zoom, you must either: Set the focal length first, before focusing. Or, remember to re-focus after zooming. Or, use AI Servo instead.
Because focus stops and locks after it's achieved in One Shot, it's a good mode if using a "focus and recompose" technique.
AI Servo is designed for use with moving subjects. Actually it's the mode to use anytime the photographer-to-subject distance changes for any reasons, or if using a zoom and changing the focal length. AI Servo never locks. It constantly measures the distance and updates focus, as long as you keep pressure on the back button or keep the shutter button half pressed, depending upon how you have the camera set up. AI Servo never locks, so there is no Focus Confirmation given. You need to learn to trust the camera and yourself. that it's working properly.
AI Servo cannot be used with "focus and recompose" technique, unless BBF is being used. If the shutter button still activates AF, it will cause the camera to refocus somewhere else, when you try to take the shot after recomposing. However if using BBF, all you have to do is lift the pressure of your thumb off the button to stop focus, allowing use of AI Servo with "focus and recompose".
AI Servo is also ideal for use with varifocal zooms... since the focus is continuously updated as the focal length of the lens is changed.
Though it can be very good, AI Servo is not quite as accurate as One Shot can be. So in critical focus situations, when possible use One Shot (Note: Live View and the separate focusing system it uses is even more accurate, although it's slower. A lot slower on most models.... 70D has new system that improves Live View focus quite a bit.)
AI Focus actually isn't a focus mode at all. It's supposed to decide for you whether or not the subject is moving, and then switch to using whichever is appropriate: One Shot or AI Servo. Frankly, I almost never use this mode. It may be better with modern cameras, but older ones where I tried it had a delay while the camera was "deciding" which mode to use, and that caused me to miss quite a few shots. Besides, I prefer to choose my own focus mode, and since I use BBF, I can simply leave my cameras in AI Servo most of the time. The mot "pro" oriented Canon models (1D series cameras) don't even have an AI Focus mode. They just have two: One Shot and AI Servo.
There are some "tweaks" to the AF systems, depending upon camera model, such as setting tracking priorities or how easily "distracted" the AF system is if something intrudes momentarily between you and the subject. Check your instruction manual for what specific fine-tuning can be done with 6D... I don't have one so can't say from experience.
There is a very helpful series of three videos about Canon auto focus systems on YouTube, posted by B&H Photo and featuring Canon USA's Rudy Winston... Each video is about half an hour long and the first is at: http://www.youtube.com/watch?v=iAx86nblZ2g Highly recommended, watch all three for additional info, even though these are a few years old now and don't specifically talk about the 6D focus system (5D Mark II's and the original 5D's AF systems are quite similar to 6D, except they have two fewer points and have 6 optional, hidden "assist" points available in AI Servo mode).
Hope this helps.
03-04-2014 02:31 PM
Alan, I'm not new to Canon, but my last Canon DSLR (a 20D) was purchased 8 yrs ago. I'm new to the 6D which appears to have at least double the menu choices. When I found "AI Servo" it had a choice of "1st image priority" which then provided 3 choices; ditto for "2nd image priority". But that was found in the menu selections. I just forgot about the top menu where I found the choices you suggested. Learning how to use these features is one side of the equation; remembering these features without use of a manual is the other side.
The 6D came with an abbreviated hard copy owner's manual and a cd containing the full manual which has 403 pages. I have the full manual copied to my pc, but navigating around such a large file is laborius to me. I plan on taking the cd to my local Fedex Office (formerly Kinkos) and having them print it out for me. Unless there's a copywright restriction?
Again, thanks for your expertise.
03-04-2014 06:56 PM
03-05-2014 12:53 PM
"When I found "AI Servo" it had a choice of "1st image priority" which then provided 3 choices; ditto for "2nd image priority". But that was found in the menu selections. I just forgot about the top menu where I found the choices you suggested. Learning how to use these features is one side of the equation; remembering these features without use of a manual is the other side."
These settings have to do with shooting in AI Servo only, and allow you to prioritize the importance of focus accuracy vs the speed of shutter release and/or drive speed (frame rate). In other words, it allows you to decide which is more important... That the image be in focus as best as possible, or that the camera take the shot as quickly as possible and with the least delay to allow for focusing.
"1st Image" is just as it sounds, whether it's a single shot or the very first shot in a burst at whatever drive speed your camera supports. The "2nd shot" setting effects the second and all subsequent shots in a continuous burst done with AI Servo while tracking the subject.
I set mine (on 7D, though it's the same effect) to maximize focus accuracy on both 1st image and 2nd/subsequent images. To me, missed focus is always going to be more of a problem than the speed of shooting. I may miss a shot occasionally if the camera slows to achieve focus (which is still far faster than I ever was back in the days of manually focused lenses), but an image that's out of focus is not going to do me much good anyway. So I set my cameras to emphasize focus accuracy as much as possible.
Possibly the more important AF "tweak" is the one entitled "Autofocus/Drive AI Servo tracking sensitivity". It's C.Fn III-1 on my 7D, maybe the same on your 6D. The name of this setting can be misleading. Setting it "slower" is often recommended, but this doesn't slow down the responsiveness of focus or the shooting speed of the camera at all. It slows how quick the AF is to jump to another point of focus. If, for example, you are tracking a moving subject using a single point and BBF, and something else passes momentarily between you and the subject, having this set toward "slow" will encourage AF to stay on the primary subject and not jump to the new (incorrect) one. It also will help keep focus on the primary subject better if you accidentally let the AF point drift off the subject momentarily.
I turn this down "slower" when I am out of practice, when I haven't been shooting a lot lately. When I am in practice (basically because I am doing a better job controlling AF with the back button) I will turn it up "faster".
The only down side of "slowing" this setting is that a more erratically moving subject, i.e. one that changes directions frequently, isn't followed as well as one that stays on the same direction of travel. "Slow" handles the latter quite well, but can be a little slow to respond when subject direction of travel changes. Turning it up "faster" does a better job with those more erratically moving subjects, I find.
It helps to know what camera you have used previously...
6D's AF is generally very similar to your 20D, except with two more AF points. Like the 20D (I used 30Ds for quite a while, which are the same), especially when shooting moving subjects in AI Servo, you will probably want to stick with the center AF point only much of the time. It's considerably more sensitive "dual axis" type in both cameras, while all the other points are "single axis" and less sensitive. For example, the center point on 6D is rated to -3EV (moonlight), while the other points are rated to approx. -1EV, if memory serves.
The camera manuals have gotten huge! To the point that they don't even provide full printed copies of them anymore.
There's a learning curve, no doubt. It can take a while to study that 400+ page manual and try out some of the different settings.
There are "guide books" you might find very helpful, too. Search or "Canon 6D" in "books" on Amazon and you'll find quite a few have been written. I always make a point of buying a guide for any new camera model I buy. These can be very useful, expanding upon what the instruction manual has to offer and significantly shortening that learning curve! Some guide book authors can recommend are Michael Guncheon, Charlotte Lowrie and David Busch. I'm sure there are some other good ones. These are just three that I'm personally familiar with.
03-06-2014 11:45 AM
Thanks for the explanation. I will print it. I did purchase David Bush's full 6D guide. It covers and explains quite a lot, but I could not find any specific set up descriptions for back button focusing. The AF-ON button was not referenced in regards to setting the camera to use it. He did cover details on various focusing settings as you explained here.
03-07-2015 05:15 PM
I followed your steps, even before I read this, but it still doesn't work. It works on my 5D, it worked on my 60D but not on my 6D. Is there any other setting that could prevent this from working?