Focus recompose using back button focus

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kabalman

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Pardon me for asking a very basic question. I have been using the back button focus for a while now. When I need to focus on a subject that is off-center, I always move the focus point on the subject and focus (using the back button focus method). While this avoids the need for me to recompose, it is not ideal for shooting quickly, as I need to keep moving the focus point on the subject for every photo.

The alternative technique, which is the focus-recompose method using the centre point focus, is giving me some issues. I used to use focus-recompose-shoot when I was focusing using the shutter button, but ever since I switched to back button focus, I am having issues (it is very likely that it is my technique that is wrong, which is where I am hoping you can help).

What I do is
1. Focus using the central focus point keeping the subject in the center using the back button.
2. Let go of the back button once focus is attained.
3. Recompose the frame by moving the subject off-center
4. Shoot - this is where I am having a problem. The camera thinks that I haven't got focus and doesn't take the shot. I get the 2 arrows (left and right facing each other) in the view finder indicating that there is no focus

What am I doing wrong? How do I use focus-recompose-shoot using the back button? Please advise.
 
That's because you're letting go of the focus button. If you let go, it will try and RE focus when you press the shutter. Focus using rear AF On.. keep it held... then recompose while keeping it held... then reshoot. The rear AF On works exactly the same as half pressing the shutter.
 
Have you changed the function of the shutter button to decouple it from focusing?

When I do this, I will half press the shutter and then press back button to focus. Then recompose with the shutter half pressed and shoot. No problems, camera knows it has focussed and shooting is easy.

Edit thinking about it based on what David just posted, I probably also keep AF on pressed too...

BUT, practice with moving focus points. It really is a better way and I'm pretty quick with it now.
 
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It would be helpful to know what camera he has, but on Nikon.. the rear AF works exactly like half pressing the shutter (unless you've changed it in custom settings). If he presses rear AF and keeps it held, he can recompose without the shutter press forcing refocus. Unless changed in custom settings, releasing rear AF and pressing the shutter will force a refocus.
 
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I think you may have left your focus coupled to the shutter button too. You don't say what camera though and I appreciate some may be different.

I always use that technique. To me, the whole point of BBF is that I don't have to hold down the focus button and risk the camera refocussing.

BTW that's not just with centre focus point, it's rare for what I need to focus on to be exactly under a focus point - that'd be composing based on FP's rather than my judgement.
 
Thanks for your replies guys. I should have mentioned that I am using a D7000. I have been doing more investigations -

These are the settings I changed -
- a1: AF-C Priority Selection to Release
- f5: Assign AE-L/AF-L Button to AF-ON

Now it does allow focus-recompose when I'm in AF-C, but still complains when in AF-A or AF-S. And my shutter has definitely been decoupled from focusing.
 
And the other point with regards to keeping the back button pressed, when under AF-C, when I recompose, it refocuses on the subject that is on the centre of the frame, thereby losing focus from the subject I initially focused on. Therefore I believe keeping the back button pressed is not going to give me the desired result.

This does work when under AF-A or AF-S.

So maybe this is how I should be doing it -

1. When shooting under AF-C, I should focus using the back button, then let go of the back button, recompose and shoot
2. When shooting under AF-A or AF-S, I should focus using the back button and keep the back button pressed while recomposing and shooting.

Is that the correct technique? Seems to work okay for me for the moment.
 
That's how I understand it. I just keep it on af-c then I have the best of both worlds, single and continuous
 
From what i remember from RTFM, You can let go of the back button after focussing and before recomposing only if you are on AF-S.

Point being is that you can focus and leave it alone (preset focus for subjects of the same distance etc) AF-C and AF-A is for things that may move or will move.
 
You can focus recompose in AF-C because you changed AF-C Priority Selection to Release. Focus priority means the camera won't take a picture if it thinks nothing is in focus while release priority means it will always take a photo when you press the shutter button.

If your camera has the option to change AF-A and AF-S to release priority then it will behave the same as when you're in AF-C mode.
 
Thanks for the replies. Just one more issue though. I see some people mention that they continue to hold the back button after recomposing and then click the shutter, this does not work for me when shooting using AF-C (continuous focus). What happens is that when I focus using the central focus point on a subject that is at the centre, then recompose and move the subject to a corner of the frame and continue to hold the back button, it just refocuses on whatever is at the centre of the new frame. The only way I can maintain the focus on the subject I originally focused on is to let go of the back button, before recomposing. Is this the correct technique under AF-C? Please advise.
 
kabalman said:
What happens is that when I focus using the central focus point on a subject that is at the centre, then recompose and move the subject to a corner of the frame and continue to hold the back button, it just refocuses on whatever is at tThanks for the replies. Just one more issue though. I see some people mention that they continue to hold the back button after recomposing and then click the shutter, this does not work for me when shooting using AF-C (continuous focus).he centre of the new frame. The only way I can maintain the focus on the subject I originally focused on is to let go of the back button, before recomposing. Is this the correct technique under AF-C? Please advise.
Click to expand...

This is how I do it on my OMD and before that all my Canons. I would focus with the back button then release the back button. Take a relevant meter reading with a half depress of the shutter button and then recompose still with the shutter still half depressed and then fully press the shutter button to take the shot. You need to ensure that your buttons are properly configured in settings for this to work

Steve
 
AF-C is for following a moving object, to utilise it for moving objects focus/recompose is useless. You have to put an active focus point over the subject.

I know some people use AF-C with BBF for static subjects, but to do that it's nuts to continue focussing.
 
Thanks, makes sense now. Agree that focus recompose is not ideal for moving subjects, so using it under AF-C is fraught with danger.
 
kabalman said:
Thanks for the replies. Just one more issue though. I see some people mention that they continue to hold the back button after recomposing and then click the shutter, this does not work for me when shooting using AF-C (continuous focus). What happens is that when I focus using the central focus point on a subject that is at the centre, then recompose and move the subject to a corner of the frame and continue to hold the back button, it just refocuses on whatever is at the centre of the new frame. The only way I can maintain the focus on the subject I originally focused on is to let go of the back button, before recomposing. Is this the correct technique under AF-C? Please advise.
Click to expand...

You need to release the back button once you have focussed and recomposed otherwise it will continue focussing on the selected af point :thumbs:
 
Use manual focus no need to recompose once it's set it stays were you set it.Or have we all forgotten how to manual focus these rubbish auto focus cameras:bonk:
 
kestral said:
Use manual focus no need to recompose once it's set it stays were you set it.Or have we all forgotten how to manual focus these rubbish auto focus cameras:bonk:
Click to expand...

These rubbish autofocus cameras weren't designed to manual focus.

Apart from some quite specific circumstances, manually focussing an AF camera is about as sensible as lighting a fire inside your microwave oven to cook your dinner.
If you want to manually focus, buy the right tools to do it with. If you buy a modern DSLR, learn to use it to its most effective, which means auto focus and understanding the metering.
 
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