Mirror Lockup

I'm experimenting with using mirror lockup on my 5D Mk III. When I enable mirror lockup, the shutter is staying open for 30 seconds, regardless of what I've set for shutter speed.

It feels like either something is defective or some other setting is kicking in that's overriding my shutter speed.

Any ideas?

Thanks

Nevermind, rereading the manual clarifies everything. For some reason I feel like the mirror lockup behavior was different with my old Canon bodies but I'm probably just going senile.

Two things. MLU is designed to move the mirror before the shutter. You have two ways to do this.
1. manually, after pressing the shutter once, wait and press again before the 30 second timer times out. THat triggers the shutter. The 30 second timer is for those that forgot what they pressed it once and forgot the second press thus reseting the camera.
2. set either the 2 or 10 second timer and it will do both shutter presses automagically. This is generally the preferred method.

Yeah, you've got to press the shutter button a second time after the mirror retracts to trip the shutter; or else use the self timer or a remote release if you have one. The second method is better since touching the shutter button kind of defeats the purpose of using MLU.

Use Live View. The mirror is up without your being blind to where the camera is pointed.