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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