Movies for TV - Early Television Foundation

144 FUNDAMENTALS
The term color correction is often heard in connection with
lenses. This does not mean that different colors are photographed
in their identical color values. It only indicates that the lens has
been corrected to ensure equal speed of light transmission for
every color. Since every color has its own individual wave length
measured in Angstrom units, it is necessary to realize that some
colors will pass through certain areas of glass more readily than
other colors and as a result will cause the focus point to occur at
a different place from other colors in the picture. This may mean
that a fuzzy or blurry picture will result since some colors focus
at the same point and others at different ones. This will mean
some of the colors will be out of focus while the others are focussed
properly. Some cameras will produce very poor pictures, while
others, identical except for the lenses, will produce excellent ones.
In the latter case the lens had been color-corrected and all colors
focussed at the same place.
Speaking
of colors and correction leads into a consideration
of filters. This is really an area for the cameraman, and anyone
desiring to make use of filters should purchase one of the many
excellent books on the subject. The Kodak Company has a really
ideal booklet which covers this field very thoroughly. The infrared
filter has already been mentioned in connection with night effects;
however, it is also much used for day work when it is necessary
to cut through a haze. In this case a red or amber filter is used for
panchromatic film, and for Kodachrome a special color filter is
advantageous. In every case, an increase in the exposure is re-
quired to compensate for the loss in light
due to the insertion of
the filter.
The Wratten filter is probably the most widely used and ;
known and for that reason will be described. In general, filters I
are not required for interior work since the light conditions can f
be adjusted to suit the emulsion used; however, on occasion it
becomes necessary to use one or more to get a special effect or si
compensate for some lighting condition which is beyond the con- <
trol of the cameraman. A filter consists of a colored film placed
on glass, or gelatin, depending on the make. It is placed over the j