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Nomenclature
Note: Whenever film velocities or time intervals on the film are given, the film run in the camera when the picture was taken is meant; the velocity of the film when being projected is not of interest here.
Symbol Description of Symbol Unit
N Any number of frames or pictures in a given part of the film frame
N' Number of shots in a burst shot
t Any time interval of film ms
ti Frame time, i.e., time value of one frame during the film ms/frame
run in the camera
T Total running time of film sec
T' Duration of a burst fired or time to be recorded sec
iiooo Any (whole) number of timing units when using 1000 tim 1 ms
ing units per second (frequency 1000)
ieo Any (whole) number of timing units when using 60 timing 16.67 ms
units per second (frequency 60)
v Velocity of film in the camera ft /sec
V Velocity of film in the camera frames/sec
Vmax Maximum film velocity near end of film run in the camera ft /sec
(Vn,ax) (frames /sec)
v_ Average film velocity over total running time ft /sec
(V) (frames/sec)
Vmu, Minimum film velocity permissible for sharp pictures ft /sec
(Vmin) (frames/sec)
n Cyclic rate of a mechanism rpm
v* Maximum velocity of moving machine part ft /sec
v* Average velocity of moving machine part over given travel ft /sec
distance
s Travel distance of machine part in.
w Width of field in the distance of moving parts covered by in.
the effective width of the film (see Fig. 3 ) (f t )
To establish the scales of this slide rule, some preparatory work, such as defining characteristic values and analyzing mathematical relationships used in the basic computations, had to be done first.
Basic Tasks for Evaluating Film Records and Formulae Used
With a given motion picture record, the relationship between a certain time interval and the corresponding number of frames is of general interest and will aid in standardizing evaluations. This time-length relationship can be indicated either by the "frame time" in ms/frame, or by the film velocity measured in ft/sec or frames/sec. Both values vary over the length of the film. This brings up the following questions:
What is the frame time, ti, at any point of the record? N frames of the film may correspond to the time t, or iiooo timing units or i6o timing units (iw and iiooo are whole numbers) ; the frame time then becomes :
t iiooo
1/1 N "N"
50
loo
3N
, inms/frame. (1)
For example: When 5 timing units of the 1000-cycles timing correspond to 8 frames, the frame time then becomes:
ti = 0.625 ms /frame.
What was the film velocity in the camera, v, in ft /sec (or V, in frames/sec), at any point of the given record? N frames may correspond to the time t, or iiooo timing units or i6o timing units, then the film velocity is :
Karl W. Maier: Slide Rule for High-Speed Data
625