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Photography Question 
Stephanie Halstead
BetterPhoto Member Since: 3/3/2005
 

mirror lock-up


Would someone help me on an explanation of this. I have a Canon 20D.


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9/29/2007 10:27:25 AM

 
Bob Cournoyer
BetterPhoto Member Since: 2/9/2003
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  How to do it or why to do it?

Bob


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9/29/2007 8:08:48 PM

 
William Schuette
BetterPhoto Member Since: 9/8/2006
  Stephanie, are you asking how you do it or why? As a Nikon shooter, I can't tell you how but for why -- 1) when your camera is mounted on a tripod and you want to minimize all camera vibration, or 2) when you need to clean your sensor.

Bill


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9/29/2007 8:09:30 PM

 
Stephanie Halstead
BetterPhoto Member Since: 3/3/2005
  Both. :)


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9/29/2007 8:09:44 PM

 
Alan N. Marcus   Hi Stephanie,

The SLR (single lens reflex) design solves many problems encountered in camera operation. The chief advantage is freedom from parallax error and the ability to focus critically while composing. Formally all cameras had a viewfinder, actually a separate optical system used to aim the camera. The viewfinder view is good for composing when the subject is distance and nearby. It’s accuracy fails at very close subject distances. Stated another way, the viewfinder view changes the position of objects as compared to the actual picture taken. The SLR design uses the exact same lens taking lens to form the composing image. This is accomplished by deflecting the light rays by means of a mirror. The mirror is hinged and motorized, it is caused to fly out of the way to take the picture and fly back so the photographer can continue to see the scene. The action is quick; you might say the camera “winks”. This quick winking movement mimics the reflex action of animal and human eye blinks. The quick shudder of the mirror cause vibrations which can induce blur at slow shutter speeds. Serious photographers, doing technical work, sometimes compose and then lock-up the mirror for the actual shot thus avoiding unnecessary internal vibration.

Technically the lens distance from the film or digital chip is about equal to the focal length of the lens. Thus telephoto lenses are long lenses set forward of the camera body while wide angle lenses are situated very close to the film or digital chip. The point within the lens, we measure from, is called the rear nodal. In modern lenses this point falls somewhere near the middle of the lens barrel. However if a super wide angle lens is mounted it might be that the rear lens element is too close to the mirror and thus will interfere with the mirror or many break the mirror when mounted. The countermeasure is to lock the mirror up to allow the super wide angle to be mounted.

Most modern wide angle lenses are often an inverted telephoto. They act like looking through a binocular backwards. This design is called a retro-focus. This design forces the rear element forward and away from the mirror.

Alan Marcus (techno babble that is often useless)
ammarcus@earthlink.net


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9/29/2007 8:21:56 PM

 
Bob Cournoyer
BetterPhoto Member Since: 2/9/2003
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  Holy cow!
On your 20D, go to menu, find mirror lock up, turn it on. Then, on the top of the camera turn on your 10 sec timer. Put your camera on a tripod. Compose/focus your picture. Push the shutter release, that will lock the mirror up and you will no longer be able to see thru the eyepiece. Then push the shutter release a second time to turn on the timer. Step away and wait. The shutter will release after 10 secs and you will not get any camera vibration from the mirror going up when the image is recorded.
It is just another camera function for timed exposures when you are trying to minimize camera vibration... :-)
Hope this helped.
Bob


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9/29/2007 8:29:40 PM

 
Stephanie Halstead
BetterPhoto Member Since: 3/3/2005
  Thank you Alan and Bob. I appreciate the your responses, both the techno and "how to". :)


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9/29/2007 8:58:18 PM

 
Alan N. Marcus   Bob, the preferred response is not “Holy Cow”, it’s "Kawabonga" I know this to be a true fact having learned it from Chief Thunderthud on the Howdy Doody. Bob, everybody knows that.

Alan Marcus


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9/29/2007 10:14:07 PM

 
Bob Cournoyer
BetterPhoto Member Since: 2/9/2003
Contact Bob
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bobslens.com
  Kawabonga!

:-)

Bob


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9/30/2007 5:50:48 AM

 
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