REPORT OF COMMISSION V GV—71 
TABLE I 
  
Type of Picture Method of Observation 
Qualitative | Quantitative 
In a motion picture projector | In a film ‘‘reader” or a ‘“‘time 
as a motion picture | and motion study" projector, 
| frame by frame 
Motion Picture (High Speed, 
Normal Speed and Time 
Lapse) 
Still Photograph | Visual observation Physical measurement of the 
amount of smear of the mov- 
ing subject 
Multiple Image Photograph 
| Visual observation Physical measurement of the 
| . . 
| distance between successive 
exposures 
Physical measurement of time 
amplitude and frequency 
Oscillograph Visual observation 
  
If d-c clutches are used for stop and start, the same voltage should be used at 
all times, so that the delay between energizing the electro-magnet and actual 
operate time is constant. The operate time should be known when millisecond 
accuracy is required. A glow-lamp can be used for calibration whenever a timing 
device is utilized. Clutches operated on a-c are more erratic because the operate 
time is dependent on the part of the sine wave on which the operate impulse is 
received. 
A number of oscillator circuits have been designed for furnishing a time 
"pip" to a glow-lamp. These vary from the crystal-controlled oscillators to 
battery-operated oscillators. Those which are battery-operated will have some 
drift, depending on the length of time that they have been left on. The charac- 
teristic frequency becomes more stable with longer operating time. The factor 
of permissible, experimental error in the analysis will be the controlling feature 
in selecting a circuit. If a 1,000 cycle oscillator is actually delivering 987 cycles, 
one millisecond (.001”) can be used for most purposes; for more accurate work, 
.001013" should be used. 
The rate at which the pictures are being made is computed from the number 
of pictures divided by the time, or in the case of a continuously moving film, 
the length of film divided by time. With cameras running at a stipulated rate, 
several conditions will affect the evaluation program: 
(1) Initial acceleration of the camera, 
(2) Steady (?) rate of the camera, and 
(3) Deceleration and stopping of the camera. 
Another phase of measurement that has not been emphasized enough is in 
the field of optics. With the use of lenses having focal lengths of 360 inches and 
600 inches, calibration of focal lengths is necessary and extremely important. 
[t is not only needed for the longer focal length lenses, but for the shorter ones 
as well. The focal length calibrations should be determined not only at tempera- 
tures of approximately 75°F.; but at —80°F., —20°F., 32°F., and 160°F. Also, 
with the increasing use of lenses in aircraft, in missiles, in the Arctic and in the 
desert and tropics, this information is necessary for accurate measurements. 
The ASA standard of +29, tolerance in stipulated focal lengths is no longer 
good enough. 
Flatness of field is also an increasingly important factor. As film bases are