Back button focus confusion discussion

[Inkanyezi]

Moving yourself forward and backward to get sharp focus? Is that how Canon shooters do it – focus with your feet?

Not just Canon, this is the technique that is most used at extreme close-up photography. It hardly involves any feet, as the movement is rather fractions of inches. As an example, the image here was shot with an enlarging lens without any focusing mechanism; just an adapter and an extension ring. The only way to focus is to move the camera into the position where focus is found.

Each of the individual flowers is about the size of a match head. The camera lies on a bean bag on the ground less than a foot from the flower. The lens is a 50 mm Rodenstock Trinar. Focusing is accomplished by nudging the camera into the right position after first placing it where the flower can be seen at all. As the camera is too close to the ground to look into the viewfinder, the articulated screen is used for framing and focusing.


purple deadnettle / paarse dovenetel

[Dave Humphries]

I would like to point out that while I agree we should avoid mis-information and mis-leading people new to photography, two of the original quotes from Andre do have 'smilies' - indicating that perhaps they shouldn't be taken too literally. (no, I don't need all the ones without smilies re-quoted!)

I hope those that 'left the room' only did so after reading my attempt to get the thread back on a productive basis in posts #44 and #52 above

[Stagecoach]

This discussion absolutely amazes me and reminds me of the lengthy discussions about RAW versus JPG. In both cases it is very straight forward to describe the differences between the two options along with the benefits and limitations in the various situations they could be used. Being a technically minded sort I would assume that would be the end of the discussion and now, armed with all the information, each person would decide what makes most sense for them and go forward. To me discussions about the facts are always worthwhile. Long discussions about opinions are generally of less value.

Back-button focus, shutter-button focus, RAW and JPG are what they are. There is no mystery here. Choose which one you like to use and worry less about justifying and convincing others why your decision is the "best" which is generally just a demonstration of ones insecurity about their decision.

John

John,

I agree with most you say but to me this thread or the track it has taken is is not one that is simply debating the merits of one way vs another.

To me it is a thread in which a significant statement was made by Andre in relation to BB focus, which was;

It should not at all be used by anybody using the focus and recompose style of shooting.

This was not a statement that infers a user simply considers a method 'better' or one that infers 'they' do something in a different or particular way. It was a statement that infers it would have a logical reason to it, it contained the term 'should' and 'not at all'.

Since this statement was made by Andre a number of posts have been made by others who spent their time producing credible information that infers the statement made by Andre is both incorrect and misleading.

Andre has not produced any credible counter debate to those posters inferring his statement was wrong and misleading or any credible facts to back up his original statement.

To me this suggests a number of possibilities to the further content and direction of this thread,

a) He will eventually produce credible facts or credible opinion to support the statement.
b) He will eventually produce credible facts or credible opinion to counter those inferring his statement was wrong.
c) He will continue to diversify from the statement producing superfluous information.
d) He will teach us something we are not aware of or have not considered.
d) He will advise us that his statement is not one to be taken seriously on a learning forum.

I await in anticipation........................

Grahame

[Mike Buckley]

Grahame,

You mentioned that you're awaiting in anticipation to learn what Andre will post in the thread. For me, the thread isn't about Andre. Instead, it's about the merits and demerits of back button focusing, when it's perhaps most helpful, when it's not helpful and even gets in the way, and to the smallest extent which cameras provide the capability. To make the thread about any individual is entirely off-topic in my mind.

[Stagecoach]

Grahame,

You mentioned that you're awaiting in anticipation to learn what Andre will post in the thread. For me, the thread isn't about Andre. Instead, it's about the merits and demerits of back button focusing, when it's perhaps most helpful, when it's not helpful and even gets in the way, and to the smallest extent which cameras provide the capability. To make the thread about any individual is entirely off-topic in my mind.

Mike,

The thread is certainly not about Andre as far as I'm concerned, it is one titled 'Back button focus confusion discussion' in which a statement has been made by Andre that comes within the realms of both discussion and confusion.

The statement is not one that constitutes a merit or demerit of BBF.

It could also be considered that someone wanting to put that sort of comment in a discussion/debate and then not addressing it when it is questioned is not dealing with the topic and hence off-topic.

Grahame

[Brownbear]

Thank you for taking the time to summarize when one might wish to use BBF so nicely. Truly appreciated.

Here are a few examples when I find BBF easier than the alternatives:

Shooting a distant stationery subject through waving grass, other foliage or fence mesh - once focused, why risk mis-focusing on the grass if the wind blows as you take subsequent shots?

With BBF:

you focus once by pushing the button you have set up for AF-ON, then simply lift your pinkie off it (focus is now locked), frame up and shoot as often as necessary, you only need to re-focus if you, or the subject, moves.

Without BBF:

you could refocus each time you take another exposure (and curse when the wind blows),
or try to keep your thumb depressing the AF-L button (be ready to curse if/when your thumb slips off)
or you could try to carefully switch the lens or camera to MF (manual focus) without losing sight of the subject hidden behind the foliage

Similar benefits to the above apply if you are shooting in low light or have an extender fitted, when AF may well struggle, or just have a lens which is slow to focus and/or likes to exercise itself from end-to-end each time you AF.



Focus and recompose, especially when using a tripod - once focused, why risk accidentally re-focusing on what happens to be under the focus point on subsequent shots?

With BBF:

you focus once by pushing the button you have set up for AF-ON, then simply lift your pinkie off it (focus is now locked), compose and shoot as many as you like, you only need to re-focus if you, or the subject, moves.

Without BBF:

you could repeat the focus and recompose actions each time you take another exposure, but you risk slightly different views each time and you may have to release tripod pan/tilt (or ball) locks to do so,
or you could try to keep your thumb depressing the AF-L button (be ready to curse if/when your thumb slips off)
or you could carefully switch the lens or camera to MF (manual focus)

Removes the need to change focus modes between AF-C (aka AI Servo) and AF-S (aka AF Single or AF One shot) via menu or multiple button pushes.

You leave the focus mode set to AF-C/AI Servo permanently, which means;

When you want auto focus to track a moving subject; you keep your pinkie on the button configured for AF-ON.
When you want AF-S (aka AF Single or AF One shot); you press and release that button
When you want Manual focus; don't press it all, just focus the lens manually (assuming that is OK for your lens, which it is for most Nikon lenses when set "M/A")

The choice of Continuous or Single (one-shot) is always instantly available.


BBF isn't always the right method, but it suits far more situations than you might initially expect, especially once your fingers/thumb/brain have got used to it.

Persevere, I'd be surprised if you don't find it worthwhile, especially if you recall doing the things listed in the "Without BBF" sections, as many, but not all, genres of photography entail.

Happy shooting, Dave

[Mike Buckley]

I missed the following detail when I first read your post, Dave.

With BBF:

you focus once by pushing the button you have set up for AF-ON, then simply lift your pinkie off it (focus is now locked), compose and shoot as many as you like, you only need to re-focus if you, or the subject, moves.

I believe that's true if the camera is configured to release the shutter whether or not the image is in focus. I configure my camera to release the shutter only when the image is in focus. As a result, I have to (want to) continue pressing the button set to AF-ON. Otherwise, the shutter may not release. Naturally, that's when using a single focusing point. EDIT: I forgot to mention that it's also when using single-servo mode, which is AF-S in Nikon-speak.

[Dave Humphries]

I believe that's true if the camera is configured to release the shutter whether or not the image is in focus. I configure my camera to release the shutter only when the image is in focus. As a result, I have to (want to) continue pressing the button set to AF-ON. Otherwise, the shutter may not release. Naturally, that's when using a single focusing point.

Hi Mike,

I'm sure I have my camera configured to only release when focus is achieved, but I don't recall the shutter not firing because the camera didn't 'think' the subject was in focus.

I wonder if that ('focus' over 'release') option is ignored under these circumstances?
Perhaps because the camera is effectively in MF mode when the AF-ON button is not pressed.

I'll try an experiment tomorrow - weather, time and (my) memory permitting.

[Dave Humphries]

Thank you for taking the time to summarize when one might wish to use BBF so nicely. Truly appreciated.

Glad to help - of course, if you get me using Iso-Auto, I'll have to nag you to try BBF for a week or two

[PhotomanJohn]

Mike & Dave

Mike's comment about needing to have focus priority turned off in order to actually do focus and recompose is fundamentally correct. In focus and recompose, we are asking the camera to focus on one point then we move to another point (presumably at a different distance or why didn't we just focus on it in the first place) and then take a picture. When I switched over to BBF on my D7000 I had to turn off AF-S and AF-C focus priority or it wouldn't take a picture when I recomposed to a point where the focus dot would be off. This all makes sense to me and agrees with what the manual says. When I got my D800 I automatically turned focus priority off on both AF-S and AF-C and didn't think anything more about it.

I was confused when you both said that you could focus and re-compose with focus priority left on so I grabbed my cameras and gave it a try. With focus priority turned on, my D7000 works as I expected and won't let me take a picture if I re-compose to an area that is not in focus which makes sense. What confuses me is that with focus priority turned on, my D800 lets me take a picture no matter what. The image can be totally out of focus and it still snaps away. This does not make sense to me and doesn't agree with the camera manual.

Any ideas while I continue my research?

John

[Mike Buckley]

I was confused when you both said that you could focus and re-compose with focus priority left on so I grabbed my cameras and gave it a try. With focus priority turned on, my D7000 works as I expected and won't let me take a picture if I re-compose to an area that is not in focus which makes sense.

Try the following: Initiate focus by pressing the back button and do NOT release the button. Recompose to a composition in which everything is absolutely out of focus. Press the shutter release button.

I just now did that using my D7000 and the shutter released, as I expected and hoped would happen. If that's not happening with your camera, there is another setting we're forgetting about that impacts the camera's operation.

What confuses me is that with focus priority turned on, my D800 lets me take a picture no matter what. The image can be totally out of focus and it still snaps away. This does not make sense to me and doesn't agree with the camera manual.

Check the pertinent camera setting just to make sure everything is as you think it is.

Alternatively, get so disgusted with your D800 that you get rid of it by sending it to me. I'll even pay the shipping charges. However, considering that you're from Sonoma County, I would appreciate a bottle of wine tossed in for good will.

[PhotomanJohn]

OK. This is another case where the manual doesn't tell the whole story. The D7000 doesn't have a AF-ON button so we reprogram the AE-L/AF-L button to do the focusing. The D800 has an AF-ON button so I guess it shouldn't be a surprise that they work differently.

With the D7000, if you have focus priority turned on, it will not let you take a picture when the subject is not in focus no matter if you are using the back button or have it configured in the standard way with shutter button focus. The only exception is if you have the lens or the camera set to manual focus then it doesn't care if the subject is in focus.

The D800 works the same way if the shutter button is used for focus (AF-ON button also initiates focus in this mode). The difference is when you disable the shutter button for focus and only use the AF-ON button, it is smart enough to automatically disable the focus priority and just takes a picture no matter what. It makes sense that Nikon would do it this way because one is likely to use focus and re-compose with BBF but it is very annoying that the wording in the two manuals are identical even though the operation of the two cameras is not.

When this thread started I thought I would only be expounding my wisdom and not actually learn anything. I was wrong. These cameras are so complicated that I will probably never know everything about them.

John

P.S. I'm keeping the D800 but will send you a bottle of wine if you give me your address

[PhotomanJohn]

Try the following: Initiate focus by pressing the back button and do NOT release the button. Recompose to a composition in which everything is absolutely out of focus. Press the shutter release button.

I just now did that using my D7000 and the shutter released, as I expected and hoped would happen. If that's not happening with your camera, there is another setting we're forgetting about that impacts the camera's operation.

Mike - Check you camera settings. It sounds like you do have focus priority turned off (i.e. set to "release").

John

[Dave Humphries]

Hi Mike,

I am testing on my D7100 (with the Nikon 70-300mm lens on) below.

Check the pertinent camera setting just to make sure everything is as you think it is.

To start from a known point, I just reconfirmed that both AF-C and AF-S modes are set to Focus priority, not Release (Custom Settings: Autofocus - a1 and a2)

Try the following: Initiate focus by pressing the back button and do NOT release the button. Recompose to a composition in which everything is absolutely out of focus. Press the shutter release button.

I was initially confused by this method/test, surely if you recompose while still holding down the button configured for AF-ON (aka BBF) - the lens will refocus when you recompose - assuming the focus point is now over something at a different distance from the camera (why wouldn't you want it to when holding the button down?).

I just tried this on the D7100 and it did what I expected (refocussed) and (of course) the shutter released (because everything was in focus).

I just now did that using my D7000 and the shutter released, as I expected and hoped would happen.

However, I have since managed to replicate your result, by setting the basic focus mode to AF-S (aka single/one shot for Canon owners).

If that's not happening with your camera, there is another setting we're forgetting about that impacts the camera's operation.

Exactly!

I always use AF-C because I want my focus to track moving subjects, typically birds, when I hold down the BBF button.
Your typical subjects do not move, explaining the choice of AF-S, I assume.


To complete the experimental options:

Switching my D7100 back to AF-C, I then (again) focussed on something about 30 feet/10m away, the fence behind that subject, at some 60 feet/20m is blurred because of limited DoF at 300mm and f/8 on a DX camera. I released the BBF button, then recomposed so only the blurry fence is framed and could still release the shutter (as many times as I liked) and all I captured was out of focus fence - again, as expected (because AF is not active).

It could therefore be argued that since I use BBF, having the settings a1 and a2 on Focus priority is silly, and this is true to a point, but those settings would be irrelevant even if they were set to Release mode while I use BBF. However, when I occasionally use normal half-press shutter button focusing, I would like the Focus priority to rule, which it does - so they'll stay as they are.


Like John, I am also learning more about how my camera works.

I am not saying using BBF with AF-S is wrong, it obviously works for you (I can see some benefit), but for my usage, it has to be used with the focus mode in AF-C (Continuous, or AI Servo for Canon shooters).

This also perhaps partly explains the differences from John's camera operation.

Mike - Check you camera settings. It sounds like you do have focus priority turned off (i.e. set to "release").

Either way, it seems that (for newer Nikons, at least) choosing AF-ON, or AF-ON only, causes the selection of focus/release priority to be ignored.

The Nikon D7100 manual (p.231 in English printing) does not mention this either - nor does the David Busch guide to the D7100. Equally, neither publication lists "BBF", "Back Button Focusing" or even "AF-ON" in their Index, no wonder Haseeb couldn't find it (earlier in this thread). The only places AF-ON is mentioned is a brief sentence or two under re-assigning a buttons (e.g. Fn or AE-L/AF-L) and that doesn't give half the facts this thread has uncovered. Little wonder there is so much internet confusion and speculation.

[Mike Buckley]

Regarding focus priority or release priority...

Either way, it seems that (for Nikon, at least) choosing AF-ON, or AF-ON only, causes the selection of focus/release priority to be ignored.

That is sort of explained or at least implied in the D7000 manual. It doesn't address the use of AF-ON but it does address what does and doesn't happen once focus has been achieved, the implication being that it doesn't matter what method is used to initiate focus. You might find the information applicable to your camera if you conduct a search on "focus priority."

[Mike Buckley]

However, I have since managed to replicate your result, by setting the basic focus mode to AF-S (aka single/one shot for Canon owners).

Sorry about causing that confusion. I forgot to mention that setting in my earlier post and have now edited the post to include it.

I am not saying using BBF with AF-S is wrong, it obviously works for you (I can see some benefit), but for my usage, it has to be used with the focus mode in AF-C (Continuous, or AI Servo for Canon shooters).

It's clear to me why we would want the behavior to be different depending on whether single-servo or continuous servo is being used, which in turn often depends on whether the subject is stationary.

[Mike Buckley]

I hope everyone by now appreciates that it's nothing less than utter nonsense for anyone to claim that we should always or never do this or that. Such a blanket statement could never come close to covering the various needs and combinations of settings that can completely change the camera's operation. It's far better that we make informed decisions about our settings in accordance with the style of photography and type of subject being considered at the time. Even then, there are often at least two combinations of settings that can result in the exact same capture.

[PhotomanJohn]

Either way, it seems that (for Nikon, at least) choosing AF-ON, or AF-ON only, causes the selection of focus/release priority to be ignored.

Dave - I would change this statement a little in that newer Nikons seem to work this way. I have noticed that the firmware in the D7100 is closer to the D800 than the D7000. As I mentioned above, the D7000 doesn't ignore AF-C or AF-S focus priority like the D7100 and the D800.

John

[Loose Canon]

I hope everyone by now appreciates that it's nothing less than utter nonsense for anyone to claim that we should always or never do this or that.

"A mind is like a parachute. It doesn't work if it is not open."
-Frank Zappa

[Mike Buckley]

With the D7000, if you have focus priority turned on, it will not let you take a picture when the subject is not in focus no matter if you are using the back button or have it configured in the standard way with shutter button focus.

It might be helpful to clarify that. Once you achieve and lock focus by holding the back button down (or presumably by holding the shutter-release button halfway down but I haven't verified that), you can then recompose. The shutter will release even if the new composition has nothing in focus. That's true whether the focus priority or the release priority is configured.