By ‘exposure’ we mean the amount of light that falls onto the film, or CCD if you are using a digital camera. In modern cameras the exposure is usually set to automatic by default and, most of the time, it can be left there and will produce beautiful pictures. There are times though, when the lighting conditions are difficult or we want to produce a particular effect and it would be nice to understand what is going on ‘under the hood’.
The problem with all types of film and recording media is that they cannot record the entire range of contrast (black to white) that the eye can see. Especially when you take into account that the eye is constantly adjusting to cope with high contrast. On a sunny day if you look into the shadows of a scene then into the bright areas, the iris in your eye will quickly adjust so you can see detail in both.
