Mirror Lockup - Why?

[jimsloy]

I'm not new to photography, but new to the 10D and digital photography. What is the purpose for mirror lockup during shooting? Or is it just for cleaning? Is it not the same as a "bulb" manual shot?

Thanks

[jduncan]

the mirror going up during a normal exposure can jolt the camera very slightly.
on a longer exposure this can lead to blurred subjects even if the camera is on a good tripod.
a way of preventing this is to compose your shot and then lock the mirror up before taking the shot.

james

[jimsloy]

OK thanks. Will try it. Could this be part of the "soft" focus issue?

[jduncan]

er no.. i dont think so

i believe some people are having problems with the camera showing rear or front focusing issues (where the focal point is either in front of or behind its intended point) although i dont have this problem myself so am unable to be more specific.
This would lead to a photo having an area of sharp focus, but just not the intended area.

camera movement would cause the whole image to be very slightly blurred.

james

[robertwgross]

The problem is often called "mirror slap" and it is a vibration inside the camera body. It shows up most during shutter speeds of maybe 1/4 second to 1/25 second. If you are shooting slower than that, the long shutter does not show that tiny bit of vibration wiggle, and it you are shooting faster than that, the quick shutter is past before the wiggle gets into the image.

---Bob Gross---