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LOYD A. JONES AND OTTO SANDVIK [j. s. M. P. E.
ture panchromatic Type 2 film developed in the standard metol hydroquinone borax formula. The most noticeable difference between these two materials from the standpoint of sound recording is the relatively low rate at which gamma increases with time in the case of the panchromatic film as compared with the par speed (orthochromatic). The rate at which contrast is changing at the point where
TABLE IV
Sensitometric Data for Motion Picture Panchromatic Type 2 Developed in M. Q.
Borax
Td
7
1
dy dTd
L
R.P.
Fog
2.0
1.00
50
0.04
4.0
0.32
2.74
0.80
3.3 +
46
0.07
8.0
0.58
2.33
0.50
3.3
44
0.12
12.0
0.77
2.28
0.37
3.1
42
0.15
20.0
0.96
2.17
0.17
2.7
41
0.19
8.3
0.60
2.32
0.48
3.2
44
0.13
gamma becomes equal to 0.6 is appreciably less in the case of the panchromatic material. It should be easier, therefore, to control contrast with the desired precision in the case of the panchromatic material. The speed of the panchromatic as indicated by the value of inertia is also much greater.
The general requirements imposed upon a photographic material for variable width recording are radically different from those demanded by the variable density methods. Here the problem is more analogous to that met in process work, such as the reproduction of a line (black and white) drawing. One portion of the sound track area should be covered by a silver deposit which is opaque, or at least very dense, while the other should receive so little exposure as to remain almost completely transparent. In other words, a very high contrast between the two areas is desired. Practical experience indicates that a density difference of from 1.3 to 1.6 (corresponding to transmission ratios of 20 and 40, respectively) is sufficient. The boundary line between the two areas should be as sharp as possible and obviously the resolving power of the material should be high. The regular motion picture positive film when developed in the formula commonly used for picture work (formula D-16) meets these requirements admirably and is the material at present in general use for variable density recording.