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Data for Technicians.
493
MEASUREMENT OF SCREEN BRIGHTNESS
Mount photometer onethird the height of screen, and take readings at each end, in the centre, and intermediately (five in all). Average of readings gives light intensity in foot-candles ; a recommended figure is from 10 to 14 foot-candles.
MISCELLANEOUS FIGURES Standard Electricity Supply (from Grid) : 230v. single-phase or 400v. three-phase, 50 cycles per second.
Accumulators : Lead-acid type, 2.6 volts per cell fully charged, specific gravity of electrolyte 1 .280 ; fully discharged 1 .8 volts per cell, specific gravity of electrolyte 1.150.
Alkaline type : 1.2 to 1.1 volts per cell.
Gas Supply : Meter reading (cubic feet) x declared value in B.T.U.s -f 100,000= therms.
Recommended Temperature of Auditorium : Winter 55° to 65° F. Summer 10° below outside temperature.
Sizes Of Posters : Double-crown : 30 in. by 20 in.
Quad-crown : 40 in. by 30 in.
Four-sheet : 60 in. by 40 in., larger sizes proportionately.
RUNNING TIME OF FILM
Standard speed of 35-mm. sound film =24 frames per second =90 ft. per minute = approximately 11 minutes per 1,000 ft.
Ft.
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
0
min.
min. 11
min. 22
min. 331
min. 441
h. m. 551
h. m. 1 61
h. m. 1 18
h. m. 1 29
h. m. 1 40
100
1
12
231
34|
451
561
1 8
1 19
1 30
1 41
200
2
13£
241
35J
461
58
1 9
1 20
1 31
1 42
300
31
2.51
361
48
59
1 10
1 21
1 32
1 431
400
41
26i
38
49
1
1 11
1 22
1 331
1 441
500
5*
16|
28
39
50
1 1
1 12
1 231
1 34^
1 451
600
6*
18
29
40
51
1 2
1 131
1 241
1 351
1 461
700
8
19
30
41
52
1 31
1 141
1 251
1 361
1 48
800
9
20
31
42
531
1 41
1 151
1 261
1 38
1 49
900
10
21
32
431
541
1 51
1 161
1 28
1 39
1 50