Mirror lockup--when does it start to be useful?

mwgrice

At what shutter speed and/or focal length (for long zooms) does mirror lockup typically start to become useful?

ian408

mwgrice wrote:

At what shutter speed and/or focal length (for long zooms) does mirror lockup typically start to become useful?

The answer is, of course, it depends.

I would suggest a rule of thumb is for any long exposure where sharpness
is dependant on little to no movement of the camera. I would likely only
use it when the camera is tripod mounted.

What mirror lockup does for you is minimize vibration induced by the
mirror as it snaps up.

For Canon cameras with MLU enabled, you'd press the shutter once to
lock the mirror up and a second time to make the exposure (of course you'd
also want to use a remote release or locking the mirror is a mute point).

LuckyBob

One thing I've read and seen demonstrated over the years (and it makes sense to me) is that MLU's effectiveness is relegated to a limited range of shutter speeds - somewhere from 1/3" to 4". While on a tripod, the shake caused by the mirror slap will diminish after a period of time. If your subject is strictly static and it's going to need a *long* exposure, the effectiveness of MLU is greatly diminished due to the fact that the vibration will only be present for a small percentage of the exposure time. That being said, I still use it a lot with long exposures; I figure if I'm going to be exposing for 20 minutes, I might as well do it right

mwgrice

Thanks, that's what I'm looking for. I had read that it doesn't really matter for long exposures, which makes sense for the reason you describe.

LuckyBob

I tried to find the most striking example I remembered over in the DPReview forums, but I couldn't. Somebody took a long-ish exposure of a skyline with a long lens, and an airplane happened to be in the field of view. The light trail (at the start of the exposure) looked like a sine wave which slowly tapered out to flat over about half the photo.

mmroden

ian408 wrote:

... is a mute point).

I think you mean 'moot point.'

http://www.worldwidewords.org/qa/qa-moo1.htm

(ducking)

ian408

mmroden wrote:

I think you mean 'moot point.'

http://www.worldwidewords.org/qa/qa-moo1.htm

(ducking)

I've been known to make spelling errors occassionally. How's about you?

LiquidAir

The other thing to note is that it gets more important the longer the lens you are using because telephoto lenses magnify the effect of camera motion.