Back Button Focus and Image Stabilizer Question

Can't seem to find the answer anywhere, so I'll pose the question: Does using the custom functions to move the AF activation to the back of the camera affect Image Stabilizer activation? I got curious when I was reading my 100mm 2.8L IS manual (page ENG-11) and it says that the image stabilizer will activate when the newly assigned focus button is pressed. So, what happens if I'm on manual focus and never touch the AF-ON button? The IS in this lens is so quiet, that I can't even tell when testing. Anyone know?

If I were you I'd want to test my set-up for the answer. Try some low shutter speeds, answer should be obvious.

Short of turning IS off, I don't believe there's a way to disable it from functioning with the shutter button half press. Its also active with what ever you have configured for AF, in addition to the shutter button.

But, yea, its pretty obvious. One, its not that quiet. And, two, you can just vibrate the camera body, and quickly see through the view finder if IS is active or not. Quick experiment will tell you for sure.

IS will engage when AF-On button is pressed and also when shutter is halfway pressed (for AE Lock/Metering)

Just tried it on my 70-200mm 2.8L IS + 40d (C.Fn IV = 3, AE Lock/Metering + AF Start) so even on an out of focus shot, when i half press the shutter button, i can hear my IS engage

JC4 wrote in post #9277230
Short of turning IS off, I don't believe there's a way to disable it from functioning with the shutter button half press. Its also active with what ever you have configured for AF, in addition to the shutter button.

But, yea, its pretty obvious. One, its not that quiet. And, two, you can just vibrate the camera body, and quickly see through the view finder if IS is active or not. Quick experiment will tell you for sure.

It helps if I turn my music off. I confirmed that it works on either mode. It's a lot quieter than my 70-200 2.8 IS.

mhthomps wrote in post #9277303
It helps if I turn my music off.

Yea, that'll do it.

But, you can always do the shake test. Try it. Half press so IS is active, and vibrate the camera while looking through the VF. Then again without IS. No comparison.

JC4 wrote in post #9277314
Yea, that'll do it.

But, you can always do the shake test. Try it. Half press so IS is active, and vibrate the camera while looking through the VF. Then again without IS. No comparison.

I don't know about you, but I try to avoid camera shake.

Jk. You're exactly right - I can definitely see the difference.

The way I'm reading your statement, it seems that Canon is reassuring you that IS will work even with the AF-ON button.

mhthomps wrote in post #9277303
It helps if I turn my music off. I confirmed that it works on either mode. It's a lot quieter than my 70-200 2.8 IS.

Just to add (and I know this thread is a week old); it's not hard at all to tell if the IS is working just by observing through the viewfinder. At 100mm without IS, look through your viewfinder and your subject will be constantly "micro-jumping" around. Half depress the shutter button and you'll instantly notice everything "smoothing out".

Is there a way to disable IS on pressing the AF-ON button? I would like the IS to engage only with the half-press of the shutter.

I frequently use BBF to focus once, then wait a while before taking a shot. This has the annoyance of having the IS triggered on two separate occasions causing unnecessary battery drain (and its just plain annoying).

noms wrote in post #17928871
Is there a way to disable IS on pressing the AF-ON button? I would like the IS to engage only with the half-press of the shutter.

I frequently use BBF to focus once, then wait a while before taking a shot. This has the annoyance of having the IS triggered on two separate occasions causing unnecessary battery drain (and its just plain annoying).

No. Just turn IS off when you're shooting in a situation where you don't want it.

I wouldn't worry too much about battery drain. But you could use a tripod for those situations where you want to wait a while before taking the shot. Then you can turn IS off completely.