We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
MANAGERS AND PROJECTIONISTS
267
values in the under 20 degree ratio column of Table 15 are less than 4. Therefore from the standpoint of distribution any one of the screens in Class A will be satisfactory for use where the angle of observation does not exceed 20 degrees. In order now to obtain the maximum average brightness within this angle for a minimum current consumption it is only necessary to choose that screen, or screens, which shows the highest value in the colurrin marked R. Next, assuming a maximum angle of 30 degrees we find that the first seven screens, Table 15, are excluded since the ratio of normal to extreme reflecting power is greater than 4. Beginning with No. 11 we may then choose screens showing the highest average reflecting power for the range 0 to 30
TABLE 17 CLASS C
20°
30°
40°
50°
No
Ratio
Rm20
Ratio
RmSO
Ratio
Rm40
Ratio
RmSO
6
1 10
79.8
1.15
77.7
1.19
76.1
1.30
74.6
35
1.10
75.3
1.14
73.5
1.20
71 7
1.23
70.4
3
1.09
65.8
1.13
64.6
1.15
63.5
1.20
62.5
4
1.10
71.2
1.13
69.6
1.16
68.3
1.19
67.3
5
1.13
85.4
1.15
83.5
1.15
82.7
1.15
82.0
1
1.03
90.0
1.05
97.9
1.08
96.8
1.12
95.5
14
1.05
71.0
1.06
71.0
1.07
70.0
1.07
67.0
20
1.06
64.0
1.09
64.0
1.10
52.0
1.10
54.0
28
1.02
71.0
1.03
70.0
1.04
70.0
1.07
69.0
2
1.03
77.1
1.05
76.2
1.05
75.6
1.06
75.0
degrees. (Author's Note : This average was found by adding together reflector powers for 0, 5, 10, 15, 20 and 30 degree angles and dividing by 6.) When the maximum angle of 40 degrees is considered we find no screen in Class A which does not exceed the limiting value of 4 for reflecting power ratio. We therefore turn to Table 16, and there find that all values of the reflecting power ratio are less than 4. We may therefore select from Class B that screen which has the highest reflecting power for the 0 to 40 degree range. L. case of the 50 degree limiting angle, three of the Class B screens are automatically excluded, and it is only necessary to select from the remainder the one having the highest average reflecting power for the 0 to 50 degree angle.