Exposure

The exhibition is a term that relates to the amount of light that is "exposed" or shone on the film in a camera when a picture is taken. When the film is properly exposed the correct amount of light struck the film by the correct amount of time.
If the film is overexposed

and too light hit the film too long. The results of overexposure in an image with detail in the lighter areas and, therefore, appear to have large spaces.
Conversely, under occur when exposed negative is light enough not been in contact with the film. Underexposed film will have more dark places that are not well defined. Many camera manuals specify the exposure latitude of the camera, the gap between under and overexposure in which the images are always on.
A photographer can manipulate the exposure for each shot, opening or closing the aperture of the camera and change the shutter speed. Most cameras come with features automatic exposure or exposure lock. Auto-exposure tends to be more useful for the fans. Experts recommend that you use the locking mechanism of exposure in high contrast light or backlight.
The meter, which measures the light in a scene are available to help a photographer to calculate the correct exposure required for a particular scene.