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Projection Engineering, September, 1929
Page 33
of observers and hence are very significant. It has been impossible thus far to obtain these hues with sufficiently low photoelectric density. Possibly further search may reveal dyes which will permit the manufacture of these hues if such seems to be necessary or desirable.
In Table I, in the column designated as "T," are the values of total transmission for these colored materials as measured visually using the reflector arc as a light source. These values are therefore a direct measure of the screen brightness obtained when using these tinted materials as compared with the screen brightness existing when using clear base positive. It will be noted that the visual transmissions of the red, orange, yellow, and yellowgreen colors are relatively high, while those of the green, blue, violet series are relatively low. This condition exists since it is desired to obtain fairly definite color saturation effects. It follows as a natural consequence of the visual sensitivity and transmission characteristics of dyes that the colors in the former group have relatively high visual transmissions for a specified color saturation, while the transmission values in the second group are in general low when a corresponding color saturation is obtained. In the last column are given short verbal descriptions of the color characteristics.
To show spectrophotometry curves for all of the seventeen members of this series seems unnecesasry, but it may be of interest to consider two or three typical cases. In Fig. 5 are «iven such curves for tint No. 1 (Rose Doree), a warm deep pink; tint No. 8 (Aquagreen), a clear blue-green; and tint No. 11 (Nocturne), a deep violetblue. Inspection of the curves shows that each of these colors has a decided density minimum throughout all or some part of that wave-length region in which the photoelectric response is maximum. The minimum density does not fall at the same wave-length in each case but shifts with the demands of the selective absorption necessary for obtaining the desired visual hue. In Table II are given data relating to the photoelectric density characteristics of these materials for potassium and caesium cells of the types in extensive use in commercial installations. Density values are designated as "D," while in the columns designated as "Db." are given the equivalent values in decibels, these representing the amplification increinenl required to compensate Cor the volume depression occasioned by the ose of these materials.
It will he noted that the specifications relative to maximum density and maximum density difference previously set forth as desirable nave been met in actual materials with a fair degree of precision. In case of the potassium cell the maximum density Is 0.28 (No. 7, Verdante), slightly less than the value of 0.80 considered
RIPGEWAY HUE. SCALE. NAME. NO
71
69 TYRIAN ROSE
67
65 TRUE PURPLE
... AMELHYST *' VIOLET
57 BLUISH VI0LET
63
59
55
>^
53 PHENYL BLUE." 49 SPECTRUM BLUE
51
47
45 CERULEAN BLUE
43
41 BENZOL GREEN 37VIVIP GREEN 33 NIGHT GREEN " 29 NEVA GREEN
39
35
31
25
GREENISH YELLOW
27
Z\ LEMON CHROME
->
I CAPMIUM YELLOW
,3 CAPMIUM ORANGE.
9 FLAME SCARLET
19
15
^>
5 SCARLET
I SPECTRUM REP
POSITIVE. FILM TVNTS NO. NAME.
16 INFERNO
15
CAPRICE
14
AMARANTH
13
FLEUR PE LIS
12
PURPLEHAZE
II
NOCTURNE
10
AZURE
<r
e
9 TURQUOISE 8 AQUAGREEN
7 VERPANTE
<r
<r
<e
^<s~
6 SUNSHINE
5 CANPLEFLAME.
4 FIRELIGHT
3 AFTERGLOW
2 PEACH&LOW
\ ROSE POREE
Fig. 4. Positions of the tints on the Ridgway Hue Scale.
allowable, while the density difference between the upper and lower Limits is 0.1!) (equivalent to 3.S decibels), also slightly less than that considered tolerable. With the caesium cell the maximum density Is exactly 0.30 (No. 13, Flour do lis), while the maximum difference Is 0.24, ool appreciably greater than the specified 0.20. The volume variation through the
entire series of seventeen tints i<
shown in Fig. 6. The ordinates Indicate the Increase In amplification expressed in decibels required In each
Cast to give the same volume oulpul
with the tint as indicated by the cumbers al the bottom of the figure, as
C pared With a sound record of
identical characteristics on the regular clear positive film, The horizontal lines are drawn at plus and minus i' decibels from the mean' of the entire group. These lines therefore define the allowable volume change as previ oualy specified, in case of the pots slum cell all <>f the tints fail between
these limits; with tl aeslum cell
two of the tints fall slightly oul Ide
these limits.
Prints have been made on nil of
these colored bases and sound repro
duction with each cell is considered satisfactory, both with respect to the increase in amplification required and
the maximum volume variation. It is
hoped thai the sound prints to be
shown B little later will demonstrate
this poinl to your satisfaction.
This concludes thai part of the
paper which may be designated as technical, dealing, as it does, with the objective or physical characteristics of tinted positive film base. The applical Ion ol these colors to a mol ton picture production Involves the consideration Of B radically different group of relationships belonging to that phase of the motion picture Industry which has been designated, tor want of heiier term, as artistry, w bile it may i>c presumptuous on the pari of the author <>f this paper to Invade a field bo remote from thai of bii accustomed activities, he feels thai there ma.\ be -'pine members of the Society more concerned with the artistic and emotional reactions than with the cold facis of scientific technology, who may be Inters ted I or perhap amused) by Borne thoughts and sugge ! Ion
'Lovd i /one*. Trant, Soc Mol Plot /'iic Wo. 18 15. 19