Mirror Lock Up....or not?

[John_Schwaller]

A few months ago, EOS Magazine published an article which leads one to question the use of mirror lock's value on very fast or long shutter speeds.

EOS Magazine is a UK publication, which I though many in other geographies might not have access to. I requested the ability to copy and post this article and yesterday received the following reply:

Hi John

Further to your e-mail, we intend to put the Mirror Lock article on our site, but in the meantime here is a pdf version for you to use. Please credit EOS magazine and our website.

Kind regards

Angela August
Editor


The EOS magazine web site is: http://www.eos-magazine.com/ They also have a forum at: http://www.eos-forums.com/

I have placed the article on 'Free File Hosting'. This is my first use of FFH, so I hpope it works OK.

http://www.freefilehosting.org/public/46051/Mirror%20lock.pdf

Anyway....I thought this might make for an interesting discussion.

John

[Bart_van_der_Wolf]

I have placed the article on 'Free File Hosting'. This is my first use of FFH, so I hpope it works OK.

I works fine.

Regarding the article, I agree with the general findings. Exposure times of approx. 1/15th of a second are most sensitive for mirror slap induced vibrations, larger mirrors requiring more dampening of the vibrations. It may be helpful to remind that Carbon fiber (and wooden) tripods also exhibit better vibration dampening.

Bart

[Walter Ash]

I works fine.

Regarding the article, I agree with the general findings. Exposure times of approx. 1/15th of a second are most sensitive for mirror slap induced vibrations, larger mirrors requiring more dampening of the vibrations. It may be helpful to remind that Carbon fiber (and wooden) tripods also exhibit better vibration dampening.

Bart

I would agree, although for safety I'll use it for up to 1/60th second exposures, or even shorter ones at focal lengths above 100mm. I've noticed a difference in the critical, 100% magnification sharpness of shots taken at 200mm and up to 1/1000th of a second. In practice this difference is minor as I'm normally not printing that big, but it illustrates the point that this isn't a "step function" where it's only needed in a certain range and irrelevant in other ranges. It's a gradual drop-off in effects.

For long exposures without point light sources you almost don't even need a cable release as long as you can press the shutter button once to open the shutter and a second time to close it (most if not all digital SLRs don't have this function, but some film cameras do). The exception is with point light sources like street lights - any minor vibration can show up even in a long exposure as these point sources are usually very intense and will leave minor trails or squigglies if the camera shakes. If it's a moonlit landscape or something and a 30 second + exposure - not necessary to worry about mirror lockup or cable release. The vibrations will dampen out before any significant exposure is made on the film or sensor.

[Aidan Weatherill]

The main reason I use mirror lockup on my 400D is that it reduces the auto timer from 10 seconds to 2 seconds :)