There is something to be said about mechanical SLR cameras; looking at the world through a sheet of glass with physical dials at your fingertips. Each dial, in turn, controlling a series of gears, springs, and levers; under tension waiting to release at any moment. Pressing the shutter to release the tension, the first curtain opens and a timer is set. When the timer winds down, the second curtain falls, slicing out a moment of time to store it in a gelatin emulsion substrate. Almost romantic.
Photographer Chris Marquardt created a short video explaining what happens in your camera every time you press the shutter, and it’s the kind of info every photographer should know.
Modern DSLRs work in a similar fashion to mechanical cameras, except they utilize electromagnets and silicon to capture the image. In the How It’s Made-esque video Marquardt demonstrates how one shutter blade will chase the other during an exposure.
When cocked, the first and second curtains are held against a spring using electromagnets. When the camera shuts off the power to the magnet, the first curtain drops and after the desired time the second curtain follows. It is something we take for granted with modern cameras, not paying too much attention unless something is wrong. An interesting side note is that your camera will use more battery power during longer exposure, as the second curtain is still being held by the magnet.
Via ISO 1200