Mirror lock-up sounds really iffy and risky, but it’s really quite simple.
Do you use an SLR?
When you look through the viewfinder, the image you see is courtesy of a mirror. When you press the shutter, the mirror has to firstly swivel up out of the way of the light path before the sensor captures the light coming through the lens – this action you see as a dark flash in the viewfinder immediately after pressing the shutter release.
When the mirror moves out of the way it slightly vibrates the camera. Not much, but more than the act of pressing the shutter release.
If you are taking a fast shot, this vibration, along with the vibration of pressing the shutter, doesn’t factor.
But for a long exposure it will reduce your clarity.
So, for the shutter release, we can use a remote release to avoid that vibration.
And for the mirror swivel vibration we can use mirror lock-up. How does it work?
When “enabled” – usually as a Custom Function, you take a photograph by pressing the remote shutter release twice.
First press and the camera goes “kerplunk!” as the mirror swivels out of the way. Second press and you hear a small “click” as the shutter opens, along with the red light appearing on the back of the camera indicating the shutter is open.
Not all digital SLRs have mirror lock-up as an option, and it is hard to do a search to create a list of the ones which do. However, as far as I can tell, the Canon EOS 20Da, released in 2005, was the first Canon digital SLR to offer it, and hence if you have a later model, eg 30D, 40D etc, they should all have it.
If you don’t have a remote shutter release, but rely on the self-timer, it seems the mirror lock-up will only work with a 2 second delay on some Canon digital SLRs, not 10 seconds. This is the case for certain at least with the Canon EOS 500D (aka Rebel T1i or Kiss Digital X3)
Originally published 16 October 2009 on Redbubble.com
Republished 11 December 2010 on Peter Hill’s Weblog