TELEVISION CAMERA OPTICS
LEARNING OBJECTIVE: Identify the optics
of a television camera.
You were introduced to the functions of camera
lenses in Chapter 11. The lenses and the associated
optics for television cameras (save viewfinder) operate in
the same manner as still photography, but we will cover
them briefly as they apply to the television medium.
The viewfinder on an ENG camera is a relatively
small television screen (1.5 inches in diameter), while a
studio camera viewfinder is larger (3 to 9 inches in
diameter). They both produce high resolution
black-and-white images. The television screen on an
ENG camera is shielded from outside reflections by a
flexible rubber eyepiece that adjusts to the operators
eye. In that rubber eyepiece, there is an adjustable lens
for you to focus since the eye is placed within an inch
or two of the screen. The studio viewfinder uses a hood
to shade the television screen from overhead studio
Within the ENG camera viewfinder, there are a
number of control lights or displays that indicate the
status of certain camera functions. Most viewfinders
automatically display information on tape status, battery
condition, tally/record light and low-light level
indicator. The viewfinders display, on command, color
bars, patterns, white/black balance setup cursor and
camera registration. All camera viewfinders are
In some camera models you may use the viewfinder
as a playback monitor for the VCR. The advantage of
this feature is that you do not need additional equipment
to set up the camera. However, some video camera
manufacturers are discontinuing this feature because
todays cameras are more reliable and recorders have
indicators to let you know when you are recording.
The lens selects a certain field of view and produces
a small, clear optical image of this view. The lens and
certain attachments are sometimes called the external
When you work with video camera lenses, you
concern yourself with the following four areas:
l Focal length
c Depth of field
As you learned in Chapter 11, focal length is the
distance from the optical center of the lens (which is not
always its physical center) to the point where the image,
as seen by the lens, is in focus.
Portable television cameras have a zoom, or
variable focal-length lens (fig. 14-8), that allows you to
select fields of view at different distances from the
camera without moving the camera. It allows you to
change the focal length of the lens from long to short or
from short to long in one continuous operation. A
complicated series of lenses interact to keep the object
in focus at all times during the zooming process.
Zooming in is the gradual changing of the lens from
a wide-angle lens to a narrow-angle lens. On the
television screen, a zoom in appears as though the
camera is moving smoothly toward the object.
Zooming out is the changing of the lens from a
close-up to a distant shot and it will appear that the
camera is moving away.
The degree to which you can change the focal length
of a zoom lens is the zoom range of your lens. The range
is often given in a ratio, such as a 10:1 zoom range. This
means you can increase your focal length 10 times.
Some cameras have a times two function, which
allows you to double the focal length at any point in the
zoom, thus making the maximum 20:1 for the above
You can control the speed of your zoom either
manually or by using a zoom servo. These features are
covered in the following text.
MANUAL ZOOM CONTROL. The manual
zoom control on ENG cameras is a small rod extending
from the zoom ring. To zoom in or out, turn the zoom
rod clockwise or counterclockwise. It takes some skill
and practice to accomplish smooth zooms with the
ZOOM SERVO. A zoom servo is nothing more
than a small motor controlled by a lever. The distance
the lever is depressed determines the speed of the zoom
typically from 2.5 to 20 seconds. The lever is called
the zoom selection or T/W switch T stands for
telephoto and W for wide angle.
There are several advantages to the zoom servo
system. Zooms are steady and smooth, especially during
slow zooms. The zoom control is easy to operate and
allows you to concentrate more on picture composition
and focusing. The zoom servo also frees the left hand to
operate the manual focus and aperture controls.