I am attempting to understand mirrorless cameras and I have read these two questions and answers:

What are the technical advantages and disadvantages of mirrorless?

Are DSLRs a dying breed, making now the time to switch to a mirrorless camera system?

and I am still a bit confused. I guess to better understand mirrorless cameras I should first fully understand what a mirror in a DSLR does and how it functions. How does the mirror in a DSLR operate?


2 Answers 2


The mirror in a DSLR reflects light from the lens into the viewfinder pentaprism, allowing you to look through the viewfinder to frame a shot. At rest, the mirror sits at an angle in front of the shutter and sensor, blocking the light from hitting them.

When you click the shutter button, the mirror lifts up, allowing the light to hit the sensor to make the shot - this is why the viewfinder goes dark while a shot is being taken (for a fraction of a second in most cases).

The mirror is also permanently raised in Live View mode, because light has to constantly hit the sensor - hence, again, the viewfinder is black in Live View mode.

This image illustrates it pretty well:

enter image description here


To complement it with some videos to see the mirror in action please have a look at the following ones among many more...




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