Exposure latitude

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For other uses, see Dynamic range (disambiguation).

Exposure latitude (or just Latitude) is the range of light intensities that a camera can capture. A camera system with a higher exposure latitude will be able to record more details in the dark and light areas of a picture. Cinematographers express the exposure latitude in terms of a number of f-stops. Exposure latitude is also sometimes referred to as film contrast ratio, luminosity range or dynamic range.

Typical exposure latitudes are:

Video camera: 5.5 stops (ratio of 45:1)
"Normal latitude" negative film: 7 stops (128:1)
"Extended latitude" negative film: 11 stops (2048:1)

In the advancement of digital cinematography, expanding the exposure latitude is a critical ingredient.

[edit] Mathematical side

The contrast of a film image is the difference between the lightest and darkest tonal densities recorded on the film. The greater the difference, the greater the contrast.

Hence, contrast may be expressed as the difference between the maximum and minimum densities of a given film:

contrast ratio = 10 power-of (Dmax - Dmin) where D is density

Alternatively, contrast may be expressed as the ratio between the maximum opacity and minimum opacity of a given film:

contrast ratio = Omax/Omin where O is opacity

These expressions for contrast ratio are entirely equivalent.

Contrast should not be confused with film gamma, which is the ratio of film density to film exposure.