Canon 300 f2.8 question

[RandySmith]

I recently purchased a new 300 f2.8, and with af = off, I have the rear * button active to engage focus, not the shutter button ... but when I depress the shutter button half-way the lens jumps as if it's trying to af .... ai servo mode or one shot doesn't change the behaviour.

Any suggestions ? Need more info ?

1dmkII, Fn settings:

00-1
01-1
02-1
04-1
05-1
06-1
07-0
08-0
09-0
10-3
11-0
12-0
13-2
14-1
15-0
16-0
17-1
18-0
19-0
20-0
21-0

[Chimper]

That would be the IS motor kicking in. Nothing to worry about.

[RandySmith]

Greg, the IS is in the "off" position on the lens ... I noticed this at first when using a monopod, with IS off .. manual focus ... thought it was kinda strange ... I sort of understand the movement during the image stabilization .... however, .....