Correct exposure may be defined as an exposure that achieves the effect the photographer intended
A more technical approach recognises that a photographic film (or sensor) has a physically limited useful exposure range, sometimes called its dynamic range.
In a very simple model, for example, out-of-range values would be recorded as "black" (underexposed) or "white" (overexposed) rather than the precisely graduated shades of colour and tone required to describe "detail.
Therefore, the purpose of exposure adjustment (and/or lighting adjustment) is to control the physical amount of light from the subject that is allowed to fall on the film, so that 'significant' areas of shadow and highlight detail do not exceed the film's useful exposure range.
This ensures that no 'significant' information is lost during capture.
In manual mode, the photographer adjusts the lens aperture and/or shutter speed to achieve the desired exposure.
Many photographers choose to control aperture and shutter independently because opening up the aperture increases exposure, but also decreases the depth of field,
A slower shutter increases exposure but also increases the opportunity for motion blur.
. Exposure_compensation|Intentionally over- or underexposing (relative to a standard or the camera's automatic exposure) is casually referred to as "exposing to the right" or "exposing to the left" respectively, as these shift the histogram of the image to the right or left.
