Mirror Lockup ... when ?

I'm noticing that the 5D Mk II is far more intolerant of camera shake, as far as IQ is concerned, than my old 50D when mounted on a tripod.

I used to revert to mirror lock up when approaching say 0.5s, but I think I need to revise that with the 5D

So my question is ... at what speed do you generally go to mirror lockup ?

Thanks in advance

Yeah, Those FF mirrors have a bit more oomph when they slap! I use MLU whenever I'm shooting landscapes on a tripod, no matter what speed I'm shooting. For action and birding, it's regular and fast SS However, I'd recommend it for SS between say, 1/60 and 5 sec or more depending to some extent on the FL of the lens...

I've read that the worst shutter speed for vibrations on a tripod are in the region of 1/10s. Much faster or slower and the vibrations have either not started or have had time to smooth out. However when I owned a decent camera that had a mirror lock-up button, I used it all the time.

With my 30D it's too much effort to set it up and I use it less than I should, maybe about 20% of the time.

The range of speed where slap can affect the image is between 1 second and 1/60.

I shoot most often in low-light situations, and my carry-around tripod is much flimsier than my 055XPROB set, so I use MLU a great amount of the time I'm shooting. It simply gives me the extra 2 seconds to ensure I'm not jiggling the tripod by being in contact with it or my camera.

I normally use mirror lock on when doing long exposures with 1/30 and below only if I am using a long lens.