Exposure refers to the amount of light falling onto the camera sensor. It is governed by two things :
- The sensitivity of the medium the light is falling on (the ISO setting of your camers).
- The length of time for which the shutter the open and the apperture size (the brightness setting of your camera.
So, if you want a bright image, either increase the ISO sensitivity or increase the brightness. Increasing ISO sensitivity reduces image quality by increasing noise. Increasing brightness reduces the image quality by reducing the shutter speed.
For a great special effect reduce the ISO sensitivity and increase the brightness to get the same effect you would get by moving the “levels” center controller in any image editting software to the left. This is because of the increased exposure time.
For a natural looking image reduce the brightness and increase the ISO sensitivity.