Basic Photography Course

Figure 13-1.Camera Sizes and Lens F-1 Lengths

8mm

16mm

35mm

Normal

12mm

25mm

50mm

Wide Angle

Telephoto

6 to 9mm

25mm and above

13 to 17mm

38mm and above

35mm or less

100mm and above

EXPOSURE CALCULATION

NOTE:

360 is a constant factor (number of degrees

AND CONTROL

in a circle).

Exposure meters for measuring incident light can be

used directly to help determine lighting ratios. A gray
card is used to get an accurate exposure reading

whenever reflected light meter readings are taken.

Incident light exposure meters are very useful for

motion pictures because they can be used at a scene to
calculate exposure before the subject arrives. They also
can be carried throughout the scene, thereby indicating
uneven lighting or "hot spots," thus indicating whether
the lighting should be altered.

With a motion-picture camera, the final exposure

adjustment is usually made only with the aperture
because fps rate of the camera determines the shutter
speed. The goal of exposure control for motion pictures
is to produce consistent and uniform image densities
and tones from one scene to the next.

Accurate and correct exposure control can be

achieved only through the proper use of a good exposure
meter. The exposure time for a movie camera is a result
of the rate at which the camera is operated (usually 24
fps) and the shutter degree opening (the degree of the

open segment of the shutter). The shutter degree opening
for a particular camera is provided by the camera
manufacturer. Given the shutter degree opening, you
can determine exposure time by use of the following
formula:

Shutter Degree Opening

360 x fps

= Exposure Time in Seconds

For example, suppose you have a camera with a

shutter degree opening of 175 degrees and you intend to
be filming at the standard rate of 24 fps. Determine the
shutter speed as follows:

Shutter Degree Opening

175

1 7 5

360 x fps

= 360 x 24= 8640 = 49

or 1/50 second

The information on exposure provided in chapter 4

applies equally well to motion-picture photography as it
does to still photography.

Neutral density filters (ND) are often used in

motion-picture work to help control exposure because
of the limited f/stop and shutter speed combinations
available on motion-picture cameras. When you are
shooting a movie, the fps and the shutter degree opening
are fixed. You may not be able to open up the aperture
to get the correct exposure control and depth of field;
therefore, you would use an ND filter to reduce the
amount of light reaching the film. Remember, because
of the fps rate, you are restricted to a given shutter speed,
and stopping the lens down would destroy your
depth-of-field effect.

MOTION VIDEO

Videotape recording has basically replaced

motion-picture film making. Motion video has a number
of advantages compared to motion-picture coverage.
Some of these advantages are as follows:

A videotape camera can record black and white

as well as color.

No time-consuming film processing is required

and recordings can be played back immediately.

When necessary videotape may be partially or

completely erased and used again for several
more recordings. It can be played back numerous
times and may be stored indefinitely.

Videotape is edited or assembled more quickly
than film.

Videotapes are duplicated and distributed easily

to other Navy activities.