E is for Exposure
Exposure is a general sense for how much light that reaches photographic film (or an image sensor, in the case of digital cameras). How much light that reaches the film is affected by:
- shutter speed
- aperture size
- amount of light illuminating the subject
Faster shutter speeds reduce the amount of light hitting the film. Larger apertures result in much more light reaching the film. Low light scenes do not put much light onto the film.
A photographer must balance these three variables with the sensitivity of the film to optimize the amount of light getting into the camera in order to get the ‘perfect’ picture. Many modern cameras (including those on cell phones) automatically adjust each of these.