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Use of filters
When light is measured through the lens the energy reduction owing to filters is generally allowed for automatically. But the various films have different sensitivities in the various spectral regions. Deviations from the measured exposure value can therefore occur with dense and extreme filters.
Thus an orange filter, for instance, requires an increase by about 1 stop value, red filters on average about 2 stop values. A completely accurate value cannot be given since the red sensitivity of
With
with our lenses measurement and settings can be carried out as with ordinary filters. With ordinary polarizing filters without circular effect the longest exposure is determined by rotation of the filter and set; now the desired effect is found and the exposure made.
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