Sequence viewing > Photographic Exposure - Resource - © Lloyd Godman

 

Exposure Latitude


Correct exposure of a photographic material or CCD, is only possible when a combination of the correct film speed and amount of light that reaches it are co-related. 

Some films have a greater exposure latitude than other films -this means that they can record a greater range of tonal information from darker tones to lighter tones. While it might be argued that the photographer does not have to be as accurate with the exposure as they might need to be with a more critical material- materials with a greater latitude have the ability to record a greater range of tones.

 

For instance consumer colour films, which are made for the mass market, have a much greater latitude than professional films. With negative films, if the film speed is too high, under exposure will occur, if it the speed is too low over exposure will occur. Incorrect exposure has a negative impact on colour density and thus colour saturation. The result is the colours will either be too dark or light and lacking in brilliance.With slide films, a deviation in sensitivity of 1 din or 1/3 of an f stop means colour densities will be reduced by 10%. Some professional films have especially low tolerances of about 1/6th of a stop.


Should I over or Under expose?

Current digital cameras have less latitude than many films - some cameras like the Fuji Pro extends the latitude by incorporating a second set of sensors. It is important to note that with digital cameras it is the information in the bright areas of the image which tend to get clipped or lost - so while it is better to expose correctly in some situations it is better to under expose than over - where as with negative film it is better to over expose than under.

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