question about back button focusing

rampanthamster

rampanthamster

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hi all, i've been reading up on this today and have decided to start using it. However, i keep reading things like this:

"recompose the frame and shoot without the camera trying to re-focus with every press of the shutter"

Now...is this assuming that i'm in af-continuous mode, and that i'm keeping my thumb pressed on the back button while doing this 'recomposing' of the shot? That's what i've been doing today using a central focus point.

So...doing this and keeping the back button held down, i'm able to move the camera about and it keeps the subject in focus. However, if i recompose the shot, i still have to make sure that the subject of the shot is in the centre of the frame, otherwise the subject will be out of focus, right?

Or am i missing the point somehow? :bonk: Many thanks
 
you don't need to use the back button for focus when re-composing. Holding the shutter butter halfway down will lock the focus, allowing you to re-compose your shot. This works for One Shot mode.

If you're in af-continuous, holding the shutter halfway, will cause the camera to try and focus on anything around your set focus point.

That how I understand it from a Canon point of view, I'm sure its the same concept the nikon too.

So, what are you trying to achieve by doing this ? Are you trying to shoot a bird in flight, or take a portrait ?

EDIT..oh, and you've understood it right too :)
 
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The OP wants to use the back button for focusing not the shutter button.

With back button focusing the shutter will never activate the AF. This means you can focus on something, recompose and then press the shutter without the camera refocusing whilst your lens is set to af.
 
hmmn, i'm trying to get away from using the half shutter press to focus though, hence moving to bb focusing.

I plan to use it for all my shots really, as it seems a bit more intuitive and people rave about it.

But yeah...i guess i still don't get the bit about being able to recompose the shot without having to refocus. As surely, once you've moved the camera about to recompose, then your initial focus is lost? So you have to focus again (albeit with the back button)

It's strange, i'm a relative newcomer to really reading up on photographic 'advanced' techniques, but i thought i was understanding a lot until this.

what's the best way to use back button focusing i suppose is what i'm primarily asking, but secondly is how does it help me recompose without refocusing. Or does it only allow this recomposing if i keep the subject at centre frame and keep the back button depressed...

thanks again :)
 
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It depends on if you are focusing on a moving subject or a stationary one.
If you are shooting a bird in flight then you'll probably need to AF it, which means compositionally you have to decide which AF point to use.
If the subject is stationary you can focus with the back button, release it then recompose and then hit the shutter without the camera re focusing.
 
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It will depend on your aperture as to the size of the DOF your are working with. If you are wide open on a 1.8 lens, then your going to have a small DOF, so any movement may make the main point go OOF. However, a very small movement, to move a persons face from centre in the shot to the bottom left half so you can see the eiffel tower behind them, will not change the focal point massively as you are still the same distance away from your subject.

so focus on somethin, centre frame and pres your back button to focus. Now recompose the frame any way you like, so that point is not centre frame. Remember the camera has no focussed on it, but on the distance it is from the camera, so anything at that exact distance will be in focus. so your origional object will still be in focus, but won't be centre frame. Now if you had the camera on a tripod, or didn't move the camera, and your subject didn't move, you could shoot as many photos as you liked, and the focus in the shots would not move. And as your not using the shutter ficus, the camera would not try to focus before every shot, so you should have less lag..


Corrections welcome, it's late!

the best thing to do is to practise and see what results you get.
 
BlackDevil said:
If the subject is stationary you can focus with the back button, release it then recompose and then hit the shutter without the camera re focusing.
Click to expand...

This is exactly what i'm trying to do. I have a little toy car on my desk right now. I have my camera set to af-s mode and single point centre focus. I focus in on the car using the back button and release, then take a shot with the shutter. Then...i recompose by moving the camera a couple of inches to the right so that the car will now be left of frame. I then try to press the shutter button to take another shot, but it won't, presumably because it's lacking focus.

If i press the back button again to focus, it just focuses on what is now in the centre of the frame. In this case my keyboard!

I'm trying a different aperture...from 4 up to 11 even.

getting majorly confused now :(
 
Aperture will be a factor to an extent - say if the DOF is low as Lawrie said. But you should be able to press the shutter button and fire the shutter, although i'm not familiar with Nikon settings so maybe a Nikon user may be able to help. Otherwise you are doing it correctly.
 
ok, i've made a bit of a break through... i'm in continuous shoot mode so basically once i focus using bb, i immidiately hold down the shutter to start firing off shots, and i am then able to move the camera, keeping the shutter held down, and in certain positions it will continue shooting and the shots are in focus..

is this just the way to do it?


edit: hmmn, scrap that really, as to be honest, shots are only being taken when the subject in in line with the central focus point. Ie, i'm changing the angle of the shot, but not really the composition.

am i right in thinking that i should be able to focus the shot of the toy car using the central focus point, then recompose so that the car is at the right of the frame, and press the shutter taking the shot without needing to refocus?? I'm using f/8 at least by the way.
 
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Back button focus should work whether you are in continuous mode or one shot mode. I think you are doing it right although you shouldn't have to keep holding the shutter button down when recomposing.
With back button focusing you can keep your AF button on the lens in the on position all the time and press the shutter without activating the lens.
 
can you recommend a simple test for me to do, to see if i get this right? Sorry for being a pain in the rear about it.

basically in a nutshell, i'm focusing on something in the middle of the frame, removing finger from bb focus, then moving the camera/recomposing so that subject is to the side of the frame, but when i press the shutter button, invariably it will refuse to take a shot..

does that not sound right?

thanks again for the help here.
 
rampanthamster said:
am i right in thinking that i should be able to focus the shot of the toy car using the central focus point, then recompose so that the car is at the right of the frame, and press the shutter taking the shot without needing to refocus?? I'm using f/8 at least by the way.
Click to expand...


This is correct and it can be applied to any of the focus points. The DOF will matter if when you have recomposed your distance between the camera and subject has changed.
 
Do you have fire when in focus set or something similar?? Other wise it will only fire when the focus point is in focus rending BBF useless turn it off and it should work
 
rampanthamster said:
basically in a nutshell, i'm focusing on something in the middle of the frame, removing finger from bb focus, then moving the camera/recomposing so that subject is to the side of the frame, but when i press the shutter button, invariably it will refuse to take a shot..

does that not sound right?

thanks again for the help here.
Click to expand...

You are doing it right but it sounds like a camera setup issue here as the shutter should fire. I don't know Nikon custom fuctions or settings so I'm afraid I can't help you on that front.
 
It's a D5000 quirk to lack a working release priority mode. I use back button focussing fine on my D700. My D5000 refuses to play ball due to it wanting to refocus after each shot. My work around is to use shutter release for focus and back button for AF lock.

See here for other people's frustrations.
 
ahhh thanks, at least i'm not going mad then. So how well does your work around work? (and how exactly)
 
After re- reading it seems it is the AEL button you are not using here,

Hold the back button focus and the camera will all be set on your focus point, but without holding the AEL button the camera will continue to attempt to alter settings for what it can see through the lens. Holding AEL while you re-compose means the camera ignores everything it would alter until you release the AEL again, this after taking your re-composed shot
 
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I agree with zilly I think your camera is set to only fire when in focus.

I use this back focus function without any problems fairly regularly but mainly shoot in manual to achieve this.

Try resetting the camera to defaults (pressing both green buttons) then single shot and manual and try maybe with a tripod so you are only concentrating on the buttons you will press and not the stability of the camera. Press the back focus button and after the camera focuses hold the AEL button down, move the camera round and while still holding the AEL button down take your shot

Hope this helps a little and I'm not teaching granny to suck eggs. ;)
 
CGeezer said:
After re- reading it seems it is the AEL button you are not using here,

Hold the back button focus and the camera will all be set on your focus point, but without holding the AEL button the camera will continue to attempt to alter settings for what it can see through the lens. Holding AEL while you re-compose means the camera ignores everything it would alter until you release the AEL again, this after taking your re-composed shot
Click to expand...

The big advantage of back button focusing is you don't need to use the AEL button. Just take your thumb of the focus button and you stop focusing. Much easier then finding AEL to retain focus on your chosen subject

This article is useful

http://www.usa.canon.com/dlc/controller?act=GetArticleAct&articleID=2286
 
Not having a Nikon I can't speak for how to set it up, but I assume you should have a setting where you can shoot without focus confirmation being obtained. I have mine camera set to continuous tracking AF without confirmation. So if I want to focus and recompose a single shot, a quick dab on the back button and I obtain focus, recompose then press the shutter. For moving subjects I just keep the back button pressed, that gives me the best of both worlds without having to change between single shot focus and continous AF.

As regards your scenario with the toy car, you are probably working at close range so more care is needed, focusing with the car at say 12" then recomposing, the camera is still focused at 12", moving the camera slightly may mean that the car is now 13" away hence slightly OOF. This is less of a problem with more distant objects, although with very wide apertures the DOF may be insufficient and the movement of the camera may mean the object is now a few inches away from the focussed point you fixed before recomposing. In that situation that is why it would pay to use an alternative focus point than always using the centre one.

I hope that helps clarify things a bit.
 
thanks again guys for all the help and advice. Unfortunately, as pointed out, it appears my nikon d5000 can't do 'proper' back button focusing, as it doesn't have a shutter release priority mode. So, i'm using a bit of a compromise, which essentially seems to do the same thing.

So if i have the ae-l button set to af lock only, I'm basically focusing by half pressing the shutter button, then holding down the back button to 'hold focus'. I'm then able to recompose and shoot at will without it refocusing, but i have to keep the back button held down. I haven't tested fully, but i think it seems to do the trick.


I don't suppose any other d5000 owners can chime in with their experiences?
 
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rampanthamster said:
I have my camera set to af-s mode and single point centre focus. I focus in on the car using the back button and release, then take a shot with the shutter. Then...i recompose by moving the camera a couple of inches to the right so that the car will now be left of frame. I then try to press the shutter button to take another shot, but it won't, presumably because it's lacking focus.
Click to expand...
You need to set the camera in af-c mode - this will allow you to shoot even if it is not in focus.

The advantage is that once set up like this you can now use either single shot or continuous focusing without having to change any settings: press the back button once to focus, then release and recompose if necessary, shoot. Or for tracking a moving object keep your thumb on the button so that it keeps re-focusing.
 
:plusone:

As Tracer says assign AE-L/AF/L button to AF-ON.

Set camera to AF-C mode and away you go.

:thumbs:
 
Once you get the BB focusing set up, just be prepared to go through a little frustration in the first couple weeks as you forget you have it set this way and wonder why the shutter release isn't focussing ;)

Went through this myself (a few times) :suspect: , but after percevering I wouldn't go back :) Although I do have one custom mode set up for shutter release firing, evaluative metering and all points focusing, just in case a situation becomes truly manic and I lose the mental ability to press more than one button at a time :D One quick turn of the mode dial fully clockwise and I'm in idiot (but safe) mode.
 
Bigvin said:
:plusone:

As Tracer says assign AE-L/AF/L button to AF-ON.

Set camera to AF-C mode and away you go.

:thumbs:
Click to expand...

this doesn't seem to work properly on the nikon d5000 though...so i have to do things differently (see post 21). But i notice you have a d5000 too and it works fine for you???

so you set those settings, and then what? Can you describe how you go about the next stage (recomposing). If i set to af-on and af-c, i make my initial focus with the back button, take finger off the back button, then take a shot.
but if i recompose TOO MUCH (ie move the camera to the side too much) then try to shoot again, it often refuses to take the shot. How exactly are you using this on your d5000? thanks
 
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rampanthamster said:
ahhh thanks, at least i'm not going mad then. So how well does your work around work? (and how exactly)
Click to expand...

Basically, my back button is set to AE/AF lock.

1) Half-press shutter release button to AF,
2) press back button to activate AF lock,
3) recompose,
4) fully depress shutter release button to take shot(s),
5) when finished then release back button.

What others don't seem to realise is that the D5000 won't open its shutter unless it's got focus lock (unless you're in manual focus mode).

As a test, I've just set my D5000

1) AE/AF lock button assigned to AF-ON,
2) pressed and released back button to focus on a subject,
3) recomposed,
4) pressed and released shutter release button.

The result is that the D5000 refuses to release the shutter. If I skip the recomposition step immediately above and just do the following:

1) AE/AF lock button assigned to AF-ON,
2) pressed and released back button to focus on a subject,
3) pressed and released shutter release button.

Then the D5000 will release the shutter.

This thread isn't just about back button focussing, it's about recomposing too.
 
rampanthamster said:
thanks again guys for all the help and advice. Unfortunately, as pointed out, it appears my nikon d5000 can't do 'proper' back button focusing, as it doesn't have a shutter release priority mode. So, i'm using a bit of a compromise, which essentially seems to do the same thing.

So if i have the ae-l button set to af lock only, I'm basically focusing by half pressing the shutter button, then holding down the back button to 'hold focus'. I'm then able to recompose and shoot at will without it refocusing, but i have to keep the back button held down. I haven't tested fully, but i think it seems to do the trick.


I don't suppose any other d5000 owners can chime in with their experiences?
Click to expand...

:plusone:

My D700 will back button focus and recompose in shutter release priority mode all day long, but my D5000 won't.
 
thanks for the post digitalRelish - i've been doing what you outlined in your first step-by-step bit and i think that seems to be the best method for us d5000 owners. Is that the method you use day-to-day? Am i right in thinking that it essentially does the same thing as traditional back button focusing on other cameras, but in a different way (ie not actually using the back button to focus, and having to keep it depressed). Am i losing anything by employing this method, other than the fact that it perhaps is not as intuitive as it ought to be...?
 
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