topic Re: 6d mk2 back button focussing in EOS DSLR & Mirrorless Cameras

6d mk2 back button focussing

Georgezx9 — Sun, 30 Dec 2018 23:06:30 GMT

Hi all, love the camera, however can anyone explain back button focussing.

the camera af-on button works as a default back button focus,

the manual states

From the manual On page 131 3rd bullet it states, that After achieving focus with on shot Af the image can be recomposed, and the focus is locked, therefore is the difference using servo ai.

I am still confused

Re: 6d mk2 back button focussing

jrhoffman75 — Mon, 31 Dec 2018 02:28:42 GMT

To have true back button focusing you need to get into custom functions and change the shutter button option to disable focusing via shutter button.

Then an you can focus via back button and when you press shutter button all you get is metering and shutter actuation.

But, until you get experience it is common to forget to press back button and you can get unfocused images.

Re: 6d mk2 back button focussing

diverhank — Mon, 31 Dec 2018 04:56:12 GMT

@Georgezx9 wrote:
Hi all, love the camera, however can anyone explain back button focussing.
the camera af-on button works as a default back button focus,
the manual states
From the manual On page 131 3rd bullet it states, that After achieving focus with on shot Af the image can be recomposed, and the focus is locked, therefore is the difference using servo ai.
I am still confused

gy

AF works differently for one shot and AI Servo modes. For one shot, once focus is achieved, as long as the focus button (AF on or Shutter button) is continued to be depressed, that focus is locked, allowing you to recompose. In AI Servo, it's very different, once focus is achieved, while holding the focus button down, the camera will continue to focus on the object that was in focus, even when it is moving away.

Page 131 describes the one-shot focus and recompose.

By default, Back button focusing, via the AF-ON button is always available and it works the same as the AF via the shutter button. In another word, it's an either or thing. The problem with this, however, is that the focus achieved by AF-On focus button is ineffective since when you press the Shutter button to take the shot, the camera refocuses, negating the focus achieved with the AF-On button. So in order to use the AF-On button focus, you need to disable the Shutter button focus - see page 497

Re: 6d mk2 back button focussing

Waddizzle — Mon, 31 Dec 2018 13:41:17 GMT

@Georgezx9 wrote:
Hi all, love the camera, however can anyone explain back button focussing.
the camera af-on button works as a default back button focus,
the manual states
From the manual On page 131 3rd bullet it states, that After achieving focus with on shot Af the image can be recomposed, and the focus is locked, therefore is the difference using servo ai.
I am still confused

gy

You do not have to reprogram the shutter button. You can focus and recompose in ONE SHOT mode, and take a photo without the camera refocusing, by simply focusing with the [AF-ON] button and holding it while you recompose. When you press the shutter, the camera will not refocus for as long as you keep holding [AF-ON] button.

You can even take multiple shots, if you wanted to. The advantage of reprogramming the shutter is that you would not have to keep pressing the [AF-ON] button.

[EDIT]

If you try this in AI SERVO mode, the camera will continuously re-focus for as long as keep pressing [AF-ON]. If you have only one AF point selected, preferably the center AF point, then the AF point will flash a focus confirmation when you first press the [AF-ON] button.

With all AF points active, you will not get a focus confirmation when you first press the button.

Re: 6d mk2 back button focussing

RobertTheFat — Mon, 31 Dec 2018 18:11:28 GMT

@Waddizzle wrote:
@Georgezx9 wrote:
Hi all, love the camera, however can anyone explain back button focussing.
the camera af-on button works as a default back button focus,
the manual states
From the manual On page 131 3rd bullet it states, that After achieving focus with on shot Af the image can be recomposed, and the focus is locked, therefore is the difference using servo ai.
I am still confused

gy
You do not have to reprogram the shutter button. You can focus and recompose in ONE SHOT mode, and take a photo without the camera refocusing, by simply focusing with the [AF-ON] button and holding it while you recompose. When you press the shutter, the camera will not refocus for as long as you keep holding [AF-ON] button.

You can even take multiple shots, if you wanted to. The advantage of reprogramming the shutter is that you would not have to keep pressing the [AF-ON] button.

[EDIT]

If you try this in AI SERVO mode, the camera will continuously re-focus for as long as keep pressing [AF-ON]. If you have only one AF point selected, preferably the center AF point, then the AF point will flash a focus confirmation when you first press the [AF-ON] button.

With all AF points active, you will not get a focus confirmation when you first press the button.

I believe it's accurate to say that holding down the AF-ON button has essentially the same effect as pressing the shutter button halfway. Some users prefer it because it avoids the possibility of accidentally activating the shutter before you mean to. But to take advantage of the AF-ON button's ability to lock focus, you have to disable the focusing capability of the shutter button. Otherwise, the shutter button will try to override the lock. (Note that this description applies in both One shot mode and AI servo mode, even though the resulting behavior differs in the two modes.)

Re: 6d mk2 back button focussing

Waddizzle — Mon, 31 Dec 2018 20:45:24 GMT

@RobertTheFat wrote:
@Waddizzle wrote:
@Georgezx9 wrote:

I believe it's accurate to say that holding down the AF-ON button has essentially the same effect as pressing the shutter button halfway.

Some users prefer it because it avoids the possibility of accidentally activating the shutter before you mean to.

But to take advantage of the AF-ON button's ability to lock focus, you have to disable the focusing capability of the shutter button. Otherwise, the shutter button will try to override the lock. (Note that this description applies in both One shot mode and AI servo mode, even though the resulting behavior differs in the two modes.)

That would be me. The problem with firing the shutter prematurely is that you will lose the focus lock. I have found it useful on occasion. I find use for it often enough that I added it as a custom shooting mode. It is perfect for focus and recompose.

An alternative is to use the change the focus point, but not every focus point works, or meters, as well as the center.

Re: 6d mk2 back button focussing

Georgezx9 — Tue, 01 Jan 2019 18:12:34 GMT

Hi all thanks for the advice.

i think I am happier, and yes I have also been pressing shutter button, and could not understand why it’s not focussing!!!!

in default mode AF ON also works as a back button focus, but only in single shot mode where it focuses on a fixed subject, and I need to recompose image

but if I want to use continuous focus on moving objects and re compose, I need to cancel shutter button focussing and re assign focus to AF ON and switch to AI servo mode, this allows me to track moving objects and re compose.

but I have to keep the moving object under the assigned focus points, which focusing area do you guys use for this, single point, allows me to track the object exactly, but difficult to track, or a larger zone means I could get false ar as as the focussing point

thoughts

Re: 6d mk2 back button focussing

Waddizzle — Tue, 01 Jan 2019 20:05:01 GMT

@Georgezx9 wrote:
Hi all thanks for the advice.
i think I am happier, and yes I have also been pressing shutter button, and could not understand why it’s not focussing!!!!
so
in default mode AF ON also works as a back button focus, but only in single shot mode where it focuses on a fixed subject, and I need to recompose image

but if I want to use continuous focus on moving objects and re compose, I need to cancel shutter button focussing and re assign focus to AF ON and switch to AI servo mode, this allows me to track moving objects and re compose.

but I have to keep the moving object under the assigned focus points, which focusing area do you guys use for this, single point, allows me to track the object exactly, but difficult to track, or a larger zone means I could get false ar as as the focussing point
thoughts
gy

Are you reading and fully understanding the previous posts in this thread?

Member diverhank has posted pages from the instruction manual for you. The pages describe how to disable focusing in the shutter button. If you do not have a copy of the instruction manual, you can download it from Canon Support on the camera's support page.

Autofocusing does not work the way you seem to think. You are mistaken about your conclusions about teh [AF-PN] button. I have already posted that the [AF-ON] button works in either ONE SHOT mode or AI SERVO mode. It does not matter which AF mode is active, which AF point is enabled, nor how many AF points are enabled.

You are also grossly underestimating the focusing and tracking features in the camera. Take a look at this recent thread.

https://community.usa.canon.com/t5/EOS/5DMkIV-AF-Settings-for-Swim-Meets/td-p/255925

The camera can easily focus on a moving subject, which means the distance to the subject is changing. The camera is also capable of tracking a moving subject, which means the subject is moving across the viewfinder. It is smart enough to identify what you are tracking by its' color, and maintain focus on it.

Tracking moving subjects with the camera is a skill that takes practice. By adjusting AF settings you can track a subject, despite objects coming between the camera and the subject. Some combinations of AF settings can cause the camera to pause refocusing when it detects an object between it and the subject.

Finally, the bad news. It probably won't work for you the first time you try to use AF tracking. It takes practice with the camera tracking subjects. It takes practice acclimating yourself to what the AF settings do, and which combinations work for what you are doing.

Re: 6d mk2 back button focussing

Georgezx9 — Tue, 01 Jan 2019 22:07:57 GMT

Hi thanks, I have read and downloaded the manual, I have already set up back button focusing, by cancelling the shutter to start focus in custom function.

i am simply trying to understand the differences between back button focusing using AF ON, and doing as above, and then how to use it effectively.

thanks

Re: 6d mk2 back button focussing

amfoto1 — Wed, 02 Jan 2019 00:30:05 GMT

Back Button Focusing (BBF) is popular among sports and wildlife photographers, in particular. Other people find it useful too. It can be used with most types of photography.

The reason BBF became popular is because it allows you to use AI Servo focus as your default auto focus mode. Separating AF from the shutter release gives you means to start and stop the focus any time you wish. To get continuous focus to follow a moving subject all you need to do is maintain continuous pressure on the button with your thumb. Or, to get the same effect as One Shot, while leaving the camera set to AI servo, all you need to do to stop continuous focusing is lift pressure off the button.

Having the camera set up with BBF and in AI Servo mode makes it possible to quickly switch between stationary and moving subjects, without having to change any camera settings.

For example, with AI Servo it's essential to use BBF when if you focus and recompose. That technique is often used to compose shots that aren't all centered on the subject, perhaps using only the center AF point. With One Shot, once focus is achieved and locked, you can recompose without concern. But if you have the camera in AI Servo mode, without BBF the camera will want to re-focus wherever you move the AF point and away from the subject, when you recompose.With BBF, all you need to do is lift your thumb off the button to stop and "lock" focus, same as with One Shot. But thanks to BBF you're ready to go back to other methods of shooting without having to stop and change any settings.

Another benefit of BBF with AI Servo is that many of today's zooms are varifocal designs.... which means they don't maintain focus when you change the focal length. If using One Shot with that type of zoom, you need to remember to cause the camera to re-focus every time you zoom the lens. You have to lift off the shutter release button then re-apply pressure (if not using BBF) or lift off the rear button and reapply it, if using it (with BBF or not). But if the camera is in AI Servo mode... which is made possible by BBF... it will immediately and automatically correct focus, without you doing anything additional.

Older Canon could be set to BBF too... but didn't have an "AF-On" button, so you had to re-assign another button to serve that purpose. Usually the * (AE Lock) button was used for that purpose. When you set that button for BBF, you were given the option to have no AE Lock or to have it occur on every shot. I usually had no AE Lock because there are other ways to accomplish the same thing on the rare occasions it's needed. Having AE Lock occur on every shot... i.e., whenever the shutter release button is half-pressed... too often caused problems for the type of photography I do.

Finally with the 40D model Canon added the AF-On button (which was fine so long as you didn't use it with the BG-E2/E2N battery grip, which was used on the 20D through 50D and didn't have an AF-On button of its own). Now with the AF-On button you essentially had BBF all the time, right from the factory.... but it won't serve the same purpose until you disable AF from the shutter release button. So that's what the above instructions have you do.

Note: The setting for the shutter release button is labelled "Meter", meaning that when you half press the shutter release the camera's metering system will start working, but not the AF system (now only activated by the AF-On button). In fact, half-press of the shutter release will also activate IS if you're using a lens with it. AND, pressing the AF-On button... even without half-press of the shutter release... will also start metering and IS.

A lot of people really like BBF once they are accustomed to it. Essentially it puts you more completely in charge of when and where the camera focuses... and it allows using AI Servo by default for both moving and stationary subjects.

The only significant drawback to BBF and AI Servo is that there's no Focus Confirmation. That only works in One Shot mode. If you think about it,, it makes sense because AI Servo runs continuously, constantly updating focus on the subject, so there really isn't anything to confirm. This can be a little disconcerting at first... you have to learn to trust the camera and yourself, rather than depend upon Focus Confirmation. The more recent cameras have a little "AF" symbol that appears in the corner of the focusing screen to let you know when AF is working and that can help (not sure if it's enabled by default or not).

By the way, you know the "beep" option with Focus Confirmation? Some people don't like it and turn it off. I don't. I leave it on because when I hear it I know I've got the camera set to One Shot mode... this alerts me to change my settings if I'm shooting moving subjects. I've used BBF and AI Servo by default for over fifteen years now.... don't use One Shot very much. So it's easy for me to forget when I've changed it (which I sometimes do when shooting portraits or macro, in particular).

When I'm shooting a sporting event it's not uncommon for me to hear other peoples' cameras beeping. I know immediately they are in the wrong focus mode and a lot of their shots of the moving subjects will miss focus because their camera's focus system locks, but the subject moves away from the point of focus before they complete taking the shot. Some systems use a different approach, with a Focus Lock button instead of an AF-On or "focus start & run" button like Canon do. I'm not sure I would get used to those.

After using BBF with AI Servo most of the time (at least 95% of the time) for all these years, I have very few missed focus shots. Rarely more than 1 or 2 percent. I also use a single AF point most of the time (this is more work for me... but really assures accurate focus). I throw away a lot of shots... but not because of missed focus problems!

Hope this helps.

***********

Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7DII (x2), 7D(x2) some other cameras, various lenses & accessories
FLICKR & ZENFOLIO

Re: 6d mk2 back button focussing

Georgezx9 — Wed, 02 Jan 2019 00:38:40 GMT

Thanks for very comprehensive and informative answer, I am more than happy now.

what caused me to look at BBF was, my wife does a lot of dog agility, and when I tried to get the dogs in focus over jumps/tunnels at speed, most shots were out of focus.

i played with this and struggled, in the end because I could never get crisp focus of the dog, as often it focused on the jump I changed my approach to give greater depth of field and hopefully catch more in focus dog, this often meant high ISO.

a friend suggested BBF as a method of keeping focus on the moving subject.

lets tryit and experiment.

Re: 6d mk2 back button focussing

jrhoffman75 — Wed, 02 Jan 2019 21:11:27 GMT

For the situation you describe my recommendation would be to use AI Servo (not AI Focus) and auto AF point selection.

See pages 132 and 140-141 in your camera manual.

See page 484 for initail focus point selection options - select a single point..

AI Servo will acquire focus at the initial point and it will follow your subject as it moves through the frame.

If you select single shot mode press BBF the camera will achieve focus on your selected subject and maintain focus as it moves. When its where you want press the shutter button.

If you select continuous shooting get your inital focus and then press the shutter. The camera will shoot multiple images.

Its important that you keep the subject within the autofocus point frame.

This guide for the 1D Mark III may be useful.

https://cpn.canon-europe.com/files/product/cameras/eos1dmark3/EOS_1D_Mark_III_Guide_to_AI_Servo_AF_Custom_Functions.pdf

Here's a tutorial video:

https://www.bing.com/videos/search?q=canon+6d+mark+ii+af+guide&view=detail&mid=C13E9D3D25075EBC4A80C13E9D3D25075EBC4A80&FORM=VIRE

Re: 6d mk2 back button focussing

Waddizzle — Wed, 02 Jan 2019 02:16:12 GMT

@Georgezx9 wrote:
Thanks for very comprehensive and informative answer, I am more than happy now.

what caused me to look at BBF was, my wife does a lot of dog agility, and when I tried to get the dogs in focus over jumps/tunnels at speed, most shots were out of focus.
i played with this and struggled, in the end because I could never get crisp focus of the dog, as often it focused on the jump I changed my approach to give greater depth of field and hopefully catch more in focus dog, this often meant high ISO.
a friend suggested BBF as a method of keeping focus on the moving subject.
lets tryit and experiment.

The problem is two fold. One is focusing a subject whose distance to the camera is changing. One is tracking a subject that is moving across the viewfinder. These are two separate, but inextricably intertwined problems. It is all too easy to conflate the two concepts.

Using BBF will not help you, at least not yet. BBF is for far more experienced users. I used to have a neighbor who trained dobermans for dog shows. He had a neat little obstacle course set up in his backyard. I think I have a pretty good idea of what you might be trying to do.

————————————-

I suggest that you select “SCN” on the shooting mode dial. Press the [Q] button, choose the leftmost menu option, which should be the default selection. Use the up/down arrows on the function disc to select “Kids” as the shooting mode.

The camera will be ready to focus and track randomly moving subjects. But, you may need to select active AF points. I suggest enabling multiple AF points to assist you with tracking the moving dogs. Keeping a single AF point on a moving subject takes lots of practice, months and years of it.

Press the [Q} button, and choose the right most menu selection. I think default is “Large Zone AF”. Use the small button [ - - - ] with the dots next to shutter to change the AF point selection option to “Large Zone AF”. There is a picture of the button icon in the menu. You might want to try “Auto Selection AF” mode, too.

What lens are you using to photograph the running and jumping dogs? How far away are you from the dogs?

Re: 6d mk2 back button focussing

Georgezx9 — Wed, 02 Jan 2019 07:48:37 GMT

Thanks, I am an experienced photographer, just new to this camera, and as always, we blame the tools first rather than my technique, however if I can maximise tool capability it will help.

The pictures vary, sometimes running straight at me, others are right to left.

again distance varies, from say 5yds to 20 yds.

my two lenses are 28-135 and 70-300 zooms, with both these when I get it right, picture quality is exceptional

Re: 6d mk2 back button focussing

amfoto1 — Wed, 02 Jan 2019 20:32:30 GMT

For action photography such as you describe I would use:

- Back Button Focusing

- Single Point AF, manually selected (usually the center point)

- AI Servo continuous focus

- USM lenses are the fastest to acquire and best tracking

- f/4 to f/8 aperture for added depth of field (minor focus error won't matter)

I use a pair of 7D Mark II, which are excellent with active subjects. Like the 1D/1DX-series cameras, 7D-series use a discrete chip to run the AF system. Dual processors handle images separately. The rest of the Canon cameras use their main processors for everything... incl. both AF and image handling. Lenses I use a lot on my 7DIIs include 70-200mm f/2.8 & f/4 (both IS, USM), 24-70mm f/2.8 USM, 28-135mm IS USM, 300mm f/2.8 IS USM, 300mm f/4 IS USM, 100-400mm IS USM "II", among others.

I typically shoot between 1000 and 4500 images at an event and have less than 1% images that miss focus... and I bet that at least half of those are my fault, not the camera's or lens'. For example, I might shoot too fast, before focus has been acquired.... or I may to keep the AF point on the subject, where I want camera & lens to focus.... or sometimes I just press the wrong button with my thumb!.... or other mistakes. It's pretty rare that I think the camera and lens miss focus.

Part of getting a high success is knowing your subjects and what they are going to do.

I haven't shot dog agility, but do shoot some similar equestrian events. A few examples:

Occasionally I'll use Expansion Points for some types of events, where the subjects change direction less predictably. Gymkhana "Pole Bending" for example, where the horse and rider zig zag through a series of poles.

I use Zone Focus occasionally too, but mostly for birds in flight, against a very distant background or clear sky.

I never use All Points/Auto. It would make for a lot of missed focus shots, I'm afraid.

Besides the camera, lens, settings and familiarity with your subjects, the other thing that's needed is practice, practice, practice! Early in the shooting season I don't get as low percentage of missed focus shots as I do later when I've been doing it a lot.

My dog photos tend to be more "posed"...

And my cats are just plain lazy!

***********

Alan Myers
San Jose, Calif., USA
"Walk softly and carry a big lens."
GEAR: 5DII, 7DII (x2), 7D(x2) some other cameras, various lenses & accessories
FLICKR & ZENFOLIO