Filters for black-and-white films
Wratten filters 8K2, 15G and 25A are intended to heighten
the contrast between different colors, translated on the film
as various shades of grey. When these filters are used, the
diaphragm aperture must be increased as compared with the
normal reading, by the following amounts :
1 stop for Wratten filter 8K2 yellow
1.5 stops » » » 15G yellow-orange
2.5 stops » » » 25A red
The effect produced by a filter varies according to the make
and sensitivity of the film and to the prevailing lighting condi-
tions. The correction factors just quoted are therefore not
absolute, but merely serve as an approximate guide.
Filters for color films
The « Skylight» filter is used to cut down exaggerated blue
overtones and to improve rendering of colors in shots made
in the shade or under overcast skies, in views of far-off land-
scapes, and snow or high-altitude scenes. No correction of
the diaphragm is needed when this filter is in use.
The « Daylight» filter is a conversion filter, and is used for
shooting films in daylight with Kodachrome Type A film
intended for artificial light. In setting the diaphragm, account
must be taken of the fact that color film designed for artificial
light, when used with the « Daylight» filter, has the same
sensitivity as daylight-type color film used without filter.
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