Mirror lock-up
 

Most dSLRs have a feature known as "Mirror Lock-Up" (MLU). Normally, the mirror inside the SLR body flips up immediately before the shutter opens. This movement causes "mirror slap", vibration caused by the mirror reaching the end of its travel and hitting the underside of the viewfinder. This vibration can cause blurring of the image as the camera body shakes from the impact.

Mirror lock-up is a mode of operation where the mirror inside the camera body flips up and is held there for a period of time (to allow the vibration to stop) before the shutter is opened.

Mirror slap blurring is most usually observed when long lenses are in use. It does however also affect relatively short focal lengths if the exposure time is long. Attached are two (100%) crops of the same scene, taken one after the other. Both are tripod mounted, using a carbon-fibre tripod which supposedly has better vibration damping than aluminium. Both are the same exposure/shutter speed/ISO settings, both are taken at the same focal length of 55mm. One image is taken just with a gentle finger on the button, the other is taken using the self timer and mirror lock-up. I was surprised by how much shake there was given the short focal length used.

Lesson learned:
For still-life, use MLU and self timer or MLU and a remote release, even at shorter lens lengths.

Duncan.

Excellent demonstration. Thanks, Duncan.

Thats really spooky - this morning I have been playing with some still life shots and (not having a remote release) have been experimenting with mirror lock and self timer, although as I started writing this post I realised I had introduced another variable - I was using a stablised lens so I have just been back a reshot with IS off.

I've used a 1/2 second shutter speed and my conclusing is that using self timer has huge impact in reducing unwanted vibrations on its own. Its also something that anyone using a non SLR camera can take advantage of.

I can't see any difference between the last two shots (w.o mirror lock & with) although as they were all saved with the same compression settings, and the last one is a slightly larger file I guess there must be slightly more detail ;) (I though the "Anti Shake" logo on my Minolta a fitting subject for this experiment :D )

Great images to show the benefit of this feature.

It is something I had on all my cameras since my first SLR in the 60's. I was most surprised when I got the D100 that this feature was missing. That has ' anti shock mode ', that puts the mirror up a couple of seconds before the shutter trips. My one wish would be for the Mirror Lock feature to be an on body control lever rather than having to cruise through the menu to access it.

I regularly use the anti shock mode even with flash.

Don

Okay im now slightly confused, i have this feature on my D50 but i always thought it was for cleaning. I guess as you have to do it a few seconds before it would not work for my photography but its great with still life/macro.

Mirror lock-up is used in cleaning but its main purpose is to eliminate shake during shutter release, as post one. For cleaning ensure the mirror is literally locked up and may only lock permanently with an external power supply connected. My Nikon in mirror lockup will release after thirty seconds which is no time for cleaning.

Ollie,

I have just downloaded the user manual for the D50. It appears at first glance that the mirror lock facility you refer to may be for cleaning the low pass filter. Page 116.

I will have a more thorough read tomorrow but as that is the only reference I can find in the index, I doubt you have a mirror up mode, and using the self timer may be the way to go. See page 100.

Don

Mirror lock up is said to be important for exposures ~ 1/15 second. Markins have an interesting document that shows vibrations as a function of time with and without MLU:

http://markins.com/charlie/report4e6.pdf

It's a bit of a sales pitch for Markins products, but still of interest.

In the past I've always used the self timer and often placed a bean bag on top of the camera. Even at 1/100 second with a 200mm lens it made a significant difference. My new Nikon camera has a mirror lock up feature, but sadly it cannot be combined with the self timer. You have to set it to MLU mode, and then use an electronic cable release. I've had one on order from Nikon for 6 weeks so hopefully it will arrive for Christmas.

Another trick for longer exposures with flash is to use rear curtain synch so that the flash fires after the mirror and shutter vibrations have had a chance to die down.

BTW if anyone knows where to get Nikon accessories without a 5+ week wait please let me know. I've an ES-1, 3T and MC-30 on order and have been waiting a couple of months in one case.

Leif

If it is as per the D70, then yes it is only for cleaning the sensor.

Leif

I rather got the impression from the manual that it is just for cleaning. But i would be interested to hear what you make of it.
And if it is for more than just cleaning i will have to get it out and have a play with it and see what happens.