What is?

[machohorn]

What exactly is "mirror lock-up"? What does it do and more specific how do I do that on my canon xsi? I have read and read my book but it is too vague for me Anyone?

[Steve Foss]

Mirror lock-up allows you to lock up the shutter mirror. At normal shutter speeds the mirror doesn't cause enough slap to affect image sharpness, but at slower shutter speeds, when you trip the shutter and the mirror slaps up, it can tremble the camera and cause blurry images. This is most commonly an issue for landscape and macro photographers who are using a tripod and stopping their apertures way down to get the best depth-of-focus possible. This causes slow shutter speeds, thus the tripod, remote shutter release, and MLU to ensure sharp images.

When MLU is engaged, your first trip of the shutter button locks up the mirrow, and you wait a second for your camera to stabilize. Then the second trip of the button opens the shutter to capture the image.

I don't have an XSi manual, but on my other camera manuals if you look in the index under "M" for mirror lock-up, you should find it if your body has that feature. It's generally one of the custom functions.

[machohorn]

Thanks Steve, next ? do you have it locked up most of the time when you are out and about or do you leave it alone just in case da big bad wolfie appears so as you do not miss that shot and only lock it up when you have the right woods setting?

[Steve Foss]

With only one body, I would only lock it up when specific conditions demand it. Because MLU requires two trips of the shutter button to take a picture, there would be off-the-cuff photos lost by leaving it enabled. And burst rate doesn't work with it enabled.

My advice was tailored to people with a single camera body. Generally, when I'm shooting macro or landscape requiring MLU, I've got one body/lens on a tripod with the remote shutter release and I leave it that way going from place to place, because I've got a second body with my telephoto and standard settings in case something develops.