Canon IS question

[LCPete]

Am I right in thinking that the IS on my 100-400 L kicks in when I focus and goes off when I take my finger off the button ?
I've got the focus assinged to the AF on button and can hear and see the IS come on when I focus, If I focus with AF on then release it, compose the shot then press the shutter , would the IS have been on when I took the shot or do I need to keep finger on the AF on until I've taken the shot ?
Hope that makes sence I'm ***p at explaining what I mean
Pete

 

[Canon Bob]

Once you've recomposed, the half-press of the shutter button to meter the shot will initiate the IS again.

Bob

 

[LCPete]

thanks Bob I havent had any problems, just wondered if I was bypassing the IS by focussing separetely with the AF on button
Pete