Today’s Question: Just read today’s Q&A about mirror lock up. Isn’t mirror lock up also used during sensor cleaning?
Tim’s Quick Answer: In a manner of speaking, yes, mirror lockup is used for sensor cleaning. The difference is that in the case of sensor cleaning mirror lockup is handled for you automatically, and is accessed separately from the actual mirror lockup feature.
More Detail: To clean the image sensor on a digital SLR, you of course need to access the actual image sensor. When the camera is not actively capturing a photo, the mirror that enables you to see through the lens will be blocking the image sensor. So, for manual sensor cleaning the mirror must be moved out of the way of the sensor.
In concept, this is very similar to the mirror lockup feature discussed in Monday’s edition of the Ask Tim Grey eNewsletter. However, in this context the mirror is moved with a different feature.
When you enable mirror lockup, you will press the shutter release button twice to capture a photo. The first time you press the shutter release button the mirror will be locked in the “up” position. The second time you press the shutter release button the photo will be captured. This enables you to delay the capture until the vibrations from the mirror movement have subsided.
When you activate the manual sensor cleaning mode for a digital SLR, the mirror will similarly be moved up and out of the way so you can access the image sensor for cleaning. This is essentially the same feature as mirror lockup, simply used in a different context. When you are finished cleaning the sensor, turning off the camera’s power will move the mirror back to the “normal” position.
Note, by the way, that when we use the term “sensor cleaning” we are really referring to cleaning the filter that is mounted in front of the actual image sensor in the camera. And as I hope goes without saying, it is critically important to be extremely careful if you choose to clean the sensor on your own camera, as there is a risk of damage that would not be covered by the warranty (or extended warranty) for your camera.