Purpose of locking the camera's mirror?

I saw someone using the term "locking the mirror" today and not 100% why you would do this? They referenced macro and cutting down vibration, but still how much vibration can be created from the camera's shutter system or mirror?

One can get perfectly good images without locking up the mirror, but if you are really after consistent, absolutely tack sharp images then every bit of vibration reduction helps. Locking up the mirror to eliminate any vibration when it slaps up makes a difference, as does using a cable release, good tripod technique and similar. In macro shooting, everything is magnified, including every little flaw and vibration. It's all about good technique. One can argue about the effectiveness of individual elements but the photographer who consistently uses those elements together will consistently get sharper shots.

Regards,
Chris

Vibration from mirror slap is more of a problem in the 1 sec to 1/60th sec shutter speed range. On bigger, long focal length lenses I can often clearly see a double image/edge when shooting at 1/15 or 1/30 on a tripod without mirror lock up.

Henry Peach wrote: Vibration from mirror slap is more of a problem in the 1 sec to 1/60th sec shutter speed range. On bigger, long focal length lenses I can often clearly see a double image/edge when shooting at 1/15 or 1/30 on a tripod without mirror lock up.

+1 on Matt's answer...Bear in mind though that not all cameras have a mirror lock up function. Some only have it for sensor cleaning. It's normally the high end cameras that do have a true mirror lock up

Some cameras include it in the timer feature.

Henry Peach wrote: Vibration from mirror slap is more of a problem in the 1 sec to 1/60th sec shutter speed range. On bigger, long focal length lenses I can often clearly see a double image/edge when shooting at 1/15 or 1/30 on a tripod without mirror lock up.

OK, I'll bite. Why is that?

Rockin Joe wrote: OK, I'll bite. Why is that?

I'm no engineer, but I think it's because at faster shutter speeds everything happens too quickly for it to be a problem, and at slower shutter speeds the vibration doesn't last long enough compared to most of the exposure. For instance if the mirror slap causes a vibration that lasts 1/15th a sec (I'm just guessing), it wouldn't expose significantly in that time compared to the whole 4 seconds of exposure; the vibration only lasts 1/60th of the entire exposure time. But if the shutter speed is 1/8th, then the vibration lasts for 1/2 the exposure.

Mirror slap may reduce sharpness at any shutter speed, but it's in the range mentioned above that I most often can see a clear double image (when pixel peeping).

If you google "mirror slap" and check out the images you'll see some examples. Cameras with large focal plane shutters, such as the Pentax 67, can even exhibit the same effect from shutter bounce. The second curtain of the shutter is big enough that when it slams to a stop it can vibrate the camera. This also is mainly only a problem in the same sort of shutter speed range.

Henry Peach wrote:

Rockin Joe wrote: OK, I'll bite. Why is that?

I'm no engineer, but I think it's because at faster shutter speeds everything happens too quickly for it to be a problem, and at slower shutter speeds the vibration doesn't last long enough compared to most of the exposure. For instance if the mirror slap causes a vibration that lasts 1/15th a sec (I'm just guessing), it wouldn't expose significantly in that time compared to the whole 4 seconds of exposure; the vibration only lasts 1/60th of the entire exposure time. But if the shutter speed is 1/8th, then the vibration lasts for 1/2 the exposure.

Mirror slap may reduce sharpness at any shutter speed, but it's in the range mentioned above that I most often can see a clear double image (when pixel peeping).

If you google "mirror slap" and check out the images you'll see some examples. Cameras with large focal plane shutters, such as the Pentax 67, can even exhibit the same effect from shutter bounce. The second curtain of the shutter is big enough that when it slams to a stop it can vibrate the camera. This also is mainly only a problem in the same sort of shutter speed range.

Crystal clear now, thanks for the help in understanding this