Hey guys, i'm having some trouble shooting at night with my 20d. I kept running into motion blur on long exposure because i was physically holding open the shutter. So i went into custom functions and changed my mirror to lockout. This solved the motion problems but after about 30 seconds after i open the mirror it closes again. Can anyone explain what's going on? thanks

I'm not a Canon user, and since no one has answered this yet I'm moving it to that forum...

I am not sure exactly what you are describing. The sequence is:

Press shutter
Mirror opens
Press shutter again
Camera takes photo and closes mirror.


If you are holding the shutter open with your finger you will always experience some camera shake, you don't say if you are using a remote release or not. Also, you don't say if you are using bulb mode. If you aren't using bulb, the longest your shutter will stay open is 30 seconds.

what you are doing is using mirror lock-up mode. this will not help you reduce blur in low light situations. what lock-up does is just lock the mirror in the upright position before the exposure starts. it waits about 5 seconds, then the shutter opens and begins exposing. after however long the exposure is, the mirror will flip back down. the feature is there for long exposures because even when you are using a tripod, the mirror flipping up can cause a bit of vibration in the camera and create blur. If the mirror flips up and waits about 5 seconds before exposing, all of the vibration will disperse in that time. If you are using a tripod, it should help with blur, but if not you need to get one. If you are in fact using bulb mode and holding the shutter button with your finger, you need to get a cable release, because this will fix your problem.