The shutter

- As we discussed earlier, your camera has two…physical mechanisms for controlling light.…It has a shutter, and an aperture.…A shutter is simply a mechanism that allows…you to control how long the image sensor…will be exposed to light.…Shutter speeds pretty intuitive.…As the shutter is open longer, more light…will strike the image sensor and your image…get brighter and brighter.…Let's go back to the pinhole camera…that we looked at earlier.…On the pinhole camera, this is the shutter…this little door here that I open and close.…When it's open, light is able to pass through…the pinhole and expose the film…that's in the back of the camera.…

So to control shutter speed, I simply…hold this door open for a longer or shorter time.…Now because the sensor on your digital camera…is so light sensitive, and because you've got…a lens to efficiently focus light onto that sensor,…your digital camera needs much…shorter exposure times than this pinhole camera.…So short in fact, that a door like this one…is impractical because there's just no way…