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dinates against the logarithms o{ the reflection factors,
a curve, as sho'"vn in Fig. 17 is obtained. The
points B, C, D, etc., represent the density values
corresponding to the areas B, C, D, etc., of the test
panels (Fig. 16). Now the density corresponding
to any of the color samples is laid ofi on the density
axis, for instance at the point M. A horizontal iine
through this point locates the point O on the curve,
and a vertical line dropped from this point to the log
reflection factor axis locates the point N. The
value of log reflection factor at the point N gives the
desired photographic reflection factor for the color in
question. In this way direct measurements o{ photographic
reflection factors, as determined in terms o{
any particular photographic material and under any
light source, may be determined easily and with fair
precision. In order to illustrate the results obtained
by this method, the data in Table I are given.
Vrsuar aNn Pnotocnepnrc (PnNcurouarrc Frru) RnruncrroN
Fecron Ver,ucs ron Coronno On-pcrs
SpectrumRed......
Vermillion.
Vermillion Orange. .
Cadmium Orange. ..
Cadmium Yellow. - -
ChromeYellow.....
(Lemon)
Apple Green. ......
Emerald Green.. . ..
Cobalt Green.. ... . .
Viridian.
Cobalt Blue.
Prussian Blue......
French Ultramarine.
Spectrum Violet....
Magenta Lake......
TABLE I
Visual
8.
14.
22.
23.
JO.
51 .
38.
JI.
t7.
16.
24
q
Il.
8.
4.
./
4.
t2.
11. ro.
8.5 t2.
12. IJ.
t2.
ro.
12.
20.
5(r.
18.
32.
18.
o.
ro.
18.
13.
ID.
+D.
16.
28.
1ry
Photographic
23.
16
l4
o. F.
72.
18.
DK
23.
25.
29.
24.
18.
12.
ra.
40.
25.
15.
6.2
l-t
o.
o-t
6.D
ID.
10
t2.
ll.
20.
DU.
18.
Ja.
20.
l.o
Mazda
Ho-
Ne.
7.8
12.
t4.
16.
21 .
22.
t7.
ro.
t2.
t4.
38.
16.
39.
22.
7.
The colors as designated in the first column refer
to pigments prepared by using Windsor and Newton
Company's oil colors. The preparation of these pigments
has been described previously, loc. cit. In
the section of the table designated as xisual are
entered the visual reflection factors of the various
colors as determined by flicker photometer measurements.
In the section o{ the table designated as
lhotographic are the reflection factor values as
measured under the various light sources as indicated.
The light sources used may be described
briefly as {ollows:
H. I.-high intensity arc.
W. F.-white flame arc.
o. F._orange flame arc.
Mazda-)ncandescent tungsten operated at color
temperature oi 3100"K.
Hg.-Cooper-Hewitt mercury vapor (standard
5O-inch U-tube).
Hg.-Ne.-combination of mercury vapor and
neon. Two standard 50-inch mercury vapor
U-tubes plus one 24-inch (780 watts) neon
tube.
t4.
K
For correct orthochromatic reproduction the photographic
reflection factor should be the same as the
visual. A comparison of the photographic values
shown in Table I with the visual values, therefore,
indicates the quality of orthochromatic rendering
obtained by using the various illuminants. It will
be noted that in case of the high intensity arc the
photographic reflection factors for the red, orange,
and yellow colors are very much too low, while
those for the blues and violets are too high. This
is in accordance with common experience and is
easily sxplrlned on the basis of the relationships
discussed in the early part o{ this paper. By using
a white flame arc the condition is improved to quite
an extent. The extreme red is still rendered much
too dark. The orange and yellow colors are rendered
more nearly as they should be. The blues,
however, are still much too high. Considering now
the values applying to the Mazd,a illumination, it
will be noted that those {or spectrum red, vermillion,
and vermillion orange are slightly higher than
they should be. From this point on, the vah.res
agree fairly well with the visual ones, although
there is a slight tendency for the blues and violets
(mixtures of red and blue) to be somewhat too
high. In the next column are shown the values
obtained using the orange flame arc. It will be
noted that these reflecting power values also agree
quite well with the visual ones, with the exception
of the blues and violets, where again the photographic
values are somewhat too high. In case of
the mercr,rry vapor all of the red, orange and yellow
colors are rendered much too dark, while the blues
and violets are too light. By using a combination
of mercury vapor and the gaseous conductor neon
lamp recently developed by the Cooper-Hewitt Electric
Company, a fair|y good color balance is obtained.
The admixture of radiation from neon,
which is concentrated largely in the long-wave portion
of the visible spectrum, brings the reflection
factors for the red, orange, and yellow colors up to
approximately their correct position on the visual
scale. There seems to be a slight tendency for
greenish yellow and green to be rendered a little
too low, while the blues and violets are somewhat
higher than they should be. On the average, however,
the rendering with this particular combination
is {airly good.
It is ve ry evident, from the values shown in
Table I, that the use of tungsten illumination with
Panchromatic motion picture film represents a
marked improvement in the truthfulness of tone
rendering as compared with that obtained by the
light sources which have been in the past most extensively
used in the motion picture studios. There
is a definite tendency, however, to produce overcorrection
in the extreme red. that is. these colors
are rendered somewhat lighter than they appear
visually. This effect can, as a matter of fact, be
noticed in practice, especially in the rendition of the
lips and flesh. This result is due, of course, to a
combination of high red sensitivity of the present
Panchromatic film and the relativelv sreat amount
ls7 l