Movies for TV - Early Television Foundation

LENSES 141
struction book for the individual camera will indicate the neces-
sary corrections to be made to maintain proper exposure.
It is very seldom that one lens will cover all the different shots
called for in a production; in fact, one might almost say "never."
Therefore, a selection of lenses is required. It is possible, of course,
to have a number of lenses and merely change them by unscrew-
ing after each shot. This would be very impractical and slow, as
well as hard on the lenses; with the constant handling, the ele-
ments might jar loose or become scratched. Therefore, a lens turret
is used which, as its name implies, is a rotating holder which
instantly places the desired lens in front of the film-gate opening
ready for filming. As many as four lenses may be accommodated
on one turret, although the usual number is three; for most cases
this is plenty. Four are usually provided for television cameras
where the number of shots in one live show may be very great and
actually require that many lenses.
The Cine Special camera which is considered by many to be
the backbone of the semi-professional cameraman's kit, has a
two-lens turret. This makes for extremely compact design and
ease of handling. Quite often when lenses are spaced very close
together, they are mounted at an angle to prevent interference
between them in the form of intrusion of the unused lens in the
picture.
Most of the other cameras in general use for substandard work
have three lenses placed on a circular turret and instantly avail-
able for use. With a proper selection of three, or even two, lenses
almost any normal production can be handled.
The "common" or "garden" lens of all work is the 25 mm or
one-inch lens, / 1.4. This focusses from one foot to infinity, and
at 15 feet covers a field of 5 feet 7 inches by 4 feet 2 inches. If it
is set for 18 inches, it covers a field 6% inches by 4% inches. Thus
it will be seen to be quite versatile; however, at 15 feet the sub-
ject is comparatively small, and for some purposes it is necessary
to have a magnified view of the subject and still remain at a dis-
tance. In this case a lens of a greater focal length is used. (The
reason for the great popularity of the one-inch lens is the fact that