Basic Photography Course

CHAPTER 13

MOTION MEDIA

Motion media has gone through many technical

advances in the past several years. Portable motion-
video cameras have changed from cumbersome
cameras and recording packs to small hand-held
cameras. Reduced size, improved quality, and easier
operation has, and is continuing to improve and
expand motion video in all areas of the Department of
Defense. Most Navy ships have closed circuit

television systems for information, entertainment,

and educational purposes. Motion media is distributed

easily and dominates all other sources of
communication in today's society. Because of this, the
Navy uses this form of communication extensively to
relay information.

The most common form of motion-media photog-

raphy is video. Since the motion picture is the grand-
father to the technology of motion media as we know
it today, it is discussed briefly in this chapter.

MOTION PICTURE

The first fact regarding motion pictures is they do

not move. Each image or frame of motion picture film

is a separate, still photograph. These individual
images or frames are normally recorded at a rate of 24
separate pictures per second. This rate can be varied
to achieve certain effects. Since so little time passes
between exposing one frame and the next, there is
relatively little difference between pictures, even
when the subject moves rapidly.

The illusion of motion in motion-picture photog-

raphy is due to the natural characteristic of human
vision. This characteristic of human vision is called

persistence of vision. Persistence of vision was

discovered by Peter Mark Roget, the author of the
famous Thesaurus. The retina of the eye continues to
perceive an image for a short period of time after the
light stimulus representing the image has been
removed. Usually, this "after image" lasts about 1/50
second, depending on the brightness of the image.

In viewing a motion picture, the eye continues to

perceive the fading image projected from one frame
as it is replaced by the next frame, and so on. In effect,

the images are momentarily superimposed in our
vision, so any differences between them, however
slight, are mentally noted. If these differences
suggest any relative change in subject position, the
apparent difference is mentally interpreted as
motion. The mind translates this information into
the logical deduction that whatever we are seeing
on the movie screen must be moving.

CAMERAS

Since motion pictures are a series of still pictures,

the motion-picture camera is basically the same as the
still-picture camera. The primary difference is that it

has a mechanism for taking a series of many
photographs in rapid succession and at regular
intervals on a ribbon of film. All cameras have the
following four basic parts: a lighttight compartment,

a lens or lenses, a shutter, and a film plane or pressure

plate.

The motion-picture camera has two additional

basic features; the film drive and intermittent action.
The film drive mechanism transports the film
continually from a supply spool of unexposed film to
a take-up spool of exposed film. This transport takes
place by means of toothed, drive sprockets. The teeth
of the drive sprockets engage the perforations along
the edge of the film and move the film through the
camera.

The intermittent action in a motion-picture

camera is caused by a pulldown claw that advanced
the film one frame at a time at the film gate.

During one cycle of operation of a motion-picture

camera, the following action takes place. The film is

advanced by the sprocket drive mechanism. The

pulldown claw or shuttle then advances the film one
frame. The film is stopped momentarily and the
shutter revolves once, thereby making the exposure.
The pulldown claw then moves the film to the next
frame for exposure. Because the film moves in an
intermittent or stop-and-go manner, it becomes
necessary to have a surplus or loops of film before
and after the pulldown claw to help take up the

13-1

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Basic Photography Course

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DOFMaster for Windows On-line Depth of Field Calculator DOFMaster for Mobile Devices On-line Depth of Field Table Hyperfocal Distance Chart Articles FAQ Recommended Books Support Contact Links Home As an Amazon Associate I earn from qualifying purchases.	contents <- previous page next page -> CHAPTER 13 MOTION MEDIA Motion media has gone through many technical advances in the past several years. Portable motion- video cameras have changed from cumbersome cameras and recording packs to small hand-held cameras. Reduced size, improved quality, and easier operation has, and is continuing to improve and expand motion video in all areas of the Department of Defense. Most Navy ships have closed circuit television systems for information, entertainment, and educational purposes. Motion media is distributed easily and dominates all other sources of communication in today's society. Because of this, the Navy uses this form of communication extensively to relay information. The most common form of motion-media photog- raphy is video. Since the motion picture is the grand- father to the technology of motion media as we know it today, it is discussed briefly in this chapter. MOTION PICTURE The first fact regarding motion pictures is they do not move. Each image or frame of motion picture film is a separate, still photograph. These individual images or frames are normally recorded at a rate of 24 separate pictures per second. This rate can be varied to achieve certain effects. Since so little time passes between exposing one frame and the next, there is relatively little difference between pictures, even when the subject moves rapidly. The illusion of motion in motion-picture photog- raphy is due to the natural characteristic of human vision. This characteristic of human vision is called persistence of vision. Persistence of vision was discovered by Peter Mark Roget, the author of the famous Thesaurus. The retina of the eye continues to perceive an image for a short period of time after the light stimulus representing the image has been removed. Usually, this "after image" lasts about 1/50 second, depending on the brightness of the image. In viewing a motion picture, the eye continues to perceive the fading image projected from one frame as it is replaced by the next frame, and so on. In effect, the images are momentarily superimposed in our vision, so any differences between them, however slight, are mentally noted. If these differences suggest any relative change in subject position, the apparent difference is mentally interpreted as motion. The mind translates this information into the logical deduction that whatever we are seeing on the movie screen must be moving. CAMERAS Since motion pictures are a series of still pictures, the motion-picture camera is basically the same as the still-picture camera. The primary difference is that it has a mechanism for taking a series of many photographs in rapid succession and at regular intervals on a ribbon of film. All cameras have the following four basic parts: a lighttight compartment, a lens or lenses, a shutter, and a film plane or pressure plate. The motion-picture camera has two additional basic features; the film drive and intermittent action. The film drive mechanism transports the film continually from a supply spool of unexposed film to a take-up spool of exposed film. This transport takes place by means of toothed, drive sprockets. The teeth of the drive sprockets engage the perforations along the edge of the film and move the film through the camera. The intermittent action in a motion-picture camera is caused by a pulldown claw that advanced the film one frame at a time at the film gate. During one cycle of operation of a motion-picture camera, the following action takes place. The film is advanced by the sprocket drive mechanism. The pulldown claw or shuttle then advances the film one frame. The film is stopped momentarily and the shutter revolves once, thereby making the exposure. The pulldown claw then moves the film to the next frame for exposure. Because the film moves in an intermittent or stop-and-go manner, it becomes necessary to have a surplus or loops of film before and after the pulldown claw to help take up the 13-1 contents Basic Photography Course <- previous page next page ->	As an Amazon Associate I earn from qualifying purchases.
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