Back Button Focusing

I know the setting to get back button focusing, but on my IS lens every time I release the button, I can see it doesn't engage the IS i.e. when I press it, the IS works but when I release it for compositional purposes it doesn't work.

How can I get the shutter button to make the IS work while BBF is working as this seems to be the only logical one to make it work?

The half-press of the shutter should engage the IS if it's set up to begin metering the scene, at least that's always been my experience.

The IS should be linked to the AF (BBF in your case) so pressing the front shutter button half way or all the way shouldn't do anything for the IS...at least that is how it would seem logical to me. I just swicthed my camera to back button focus and have been using primes for the past week, and can't say that I thought much of the IS. I'll pop another lens on later and see if my assumptions are right.

RichSoansPhotos wrote in post #14976331
I know the setting to get back button focusing, but on my IS lens every time I release the button, I can see it doesn't engage the IS i.e. when I press it, the IS works but when I release it for compositional purposes it doesn't work.

How can I get the shutter button to make the IS work while BBF is working as this seems to be the only logical one to make it work?

I don't follow you. Can you be more specific? You say that when you press the back button, the IS works. What more are you wanting? Do you mean to say that when you release the button, you expect the IS to shut off?

Using BBF, when you press the button to focus, the IS will activate. If you don't BBF and you just press the shutter button, the IS will also activate. Either button will activate the IS as long as the IS is in the ON setting on the lens itself.

But different lenses have different characteristics when it comes to the IS shutting off. Some lenses will shut off the IS after a second or two after you release the shutter or AF/On button and then will re-engage it at the moment you place your finger on the shutter button. Other lenses will leave the IS on for up to a minute after you release the button before the IS is shut off. Some may be even longer but the longest I have experienced is the SIgma 17-70 f2.8-4 OS Macro that takes a full minute before the IS shuts off. So if you BBF and the IS kicks on and then you spend 30-40 seconds composing and then when you go to press the shutter button you may not hear the IS engage because it never shut off in the first place.

If you don't think this answers your question, then reply back with some more details such as the camera model, the specific lens and we can do some troubleshooting.

kfreels wrote in post #14976502
I don't follow you. Can you be more specific? You say that when you press the back button, the IS works. What more are you wanting? Do you mean to say that when you release the button, you expect the IS to shut off?

No I don't expect it to shut off, it feels like it shuts off by me releasing the BBF

I guess I have to practice half pressing the shutter button again, thanks

Its a lot less than a split second that I've experienced the IS shutting off
I use the 70-200mm IS 2.8L MKII lens

I didn't have the time to try this out in the field, but I was using the 5DMKII at the time

RichSoansPhotos wrote in post #14976674
No I don't expect it to shut off, it feels like it shuts off by me releasing the BBF



I guess I have to practice half pressing the shutter button again, thanks

But different lenses have different characteristics when it comes to the IS shutting off. Some lenses will shut off the IS after a second or two after you release the shutter or AF/On button and then will re-engage it at the moment you place your finger on the shutter button. Other lenses will leave the IS on for up to a minute after you release the button before the IS is shut off. Some may be even longer but the longest I have experienced is the SIgma 17-70 f2.8-4 OS Macro that takes a full minute before the IS shuts off. So if you BBF and the IS kicks on and then you spend 30-40 seconds composing and then when you go to press the shutter button you may not hear the IS engage because it never shut off in the first place.

Its a lot less than a split second that I've experienced the IS shutting off
I use the 70-200mm IS 2.8L MKII lens

I didn't have the time to try this out in the field, but I was using the 5DMKII at the time

OK. The 70-200 shuts off in just a second after you release the button. But either button - the AF/ON or the shutter should activate it. I don't have that particular lens so I can't comment on how it sounds when it activates and shuts off. It may just be really quiet.

I would do some controlled tests just to see if the problem can be more clearly identified. To do this, we'll leave the BBF entirely out of the equation. Leave the camera on BBF, but take some shots at 200mm manually focusing, making certain you don't accidentally hit the back button. Do some with the IS off and with the IS on and see if you can tell any difference in the sound or sharpness.

What's your shutter button actually set to? Is it still set on both AF start and meter start? If you're using BBAF you can leave the AF-ON button to AF and unassign focus duty to the shutter, and leave it simply to start metering on half press. I don't have the 70-200, but on my 17-55 and 100-200 IS lenses, the half press metering start will engage the lens's IS system. So in your case you can still release the AF-ON button if you wish to focus-recompose, and do the shutter half-press to keep IS engaged, and as long as AF isn't assigned to half-shutter it won't alter your original focus.

ceremus wrote in post #14976949
What's your shutter button actually set to? Is it still set on both AF start and meter start? If you're using BBAF you can leave the AF-ON button to AF and unassign focus duty to the shutter, and leave it simply to start metering on half press. I don't have the 70-200, but on my 17-55 and 100-200 IS lenses, the half press metering start will engage the lens's IS system. So in your case you can still release the AF-ON button if you wish to focus-recompose, and do the shutter half-press to keep IS engaged, and as long as AF isn't assigned to half-shutter it won't alter your original focus.

Agreed here. I thought that was already mentioned above but apparently not. That's how mine is setup - shutter half-press is meter start and I know both the metering and AF will activate the IS. So if the OP has BBF on AF/Meter start and has the shutter half-press unassigned as you say then this would be the result.

So to the OP - in basic terms, you have a couple options with BBF. You can have it on AF start or AF/Meter start. Choose the AF start only and have the Meter start on the shutter half-press. If that doesn't change it, then we'll continue troubleshooting.

OK, thanks for all the help, will do some more tests

RichSoansPhotos wrote in post #14977881
OK, thanks for all the help, will do some more tests

I had the same issue, and people swore that I was crazy... After a bit of poking around, I found that if you have IS-Start assigned to a button that the metering start that the back button AF will not activate IS. Once I removed that from it's own button it worked as I expected, get IS from back button, or half shutter press (and keep holding). Maybe you have similar settings?

Tested the new setting, thanks again

Hey Guys,

Can you please link me to some thread that explains BBF in detail?

^
http://www.learn.usa.c​anon.com …ckbutton_af_art​icle.shtml

Thanks David.

JasonMK wrote in post #14976431
The IS should be linked to the AF (BBF in your case) so pressing the front shutter button half way or all the way shouldn't do anything for the IS...at least that is how it would seem logical to me. I just swicthed my camera to back button focus and have been using primes for the past week, and can't say that I thought much of the IS. I'll pop another lens on later and see if my assumptions are right.

Thats not how mine works. I am set for BBF and the shutter only monitors the scene. If I press just the shutter button, the IS engages just like it does when pressing the BBF. All of my bodies have done this.