An integrating sphere type of physical densitometer has been developed with a view to standardizing density measurements in the motion picture industry. The instrument accommodates films or plates up to 5″ wide. Scanning beam dimensions of 0.025″×0.100″ are used but may readily be changed. Density values corresponding to (1) the equivalent of standard visual diffuse or (2) photographic printing density may be obtained by insertion of suitable optical filters. Densities up to 3.0 are read directly on a special three‐scale logarithmic meter which provides a uniform density scale. A chopper in the light path makes possible a.c. amplification using a highly stabilized amplifier with a highly selective gain‐frequency characteristic. This latter feature permits operation in daylight or in a room illuminated with ordinary a.c. lamps. Calibration is based on the inverse square law.

1.
L. A.
Jones
, “
A motion picture laboratory sensitometer
,”
J. Soc. Mot. Pict. Eng.
17
,
536
(
1931
).
Google Scholar
 
2.
W. W.
Lindsay
, Jr., and
W. V.
Wolfe
, “
A wide range linear scale photoelectric cell densitometer
,”
J. Soc. Mot. Pict. Eng.
28
,
622
(
1937
).
Google Scholar
 
3.
F.
Hurter
 and
V. C.
Driffield
, “
Photo‐chemical investigations and a new method of determination of the sensitiveness of photographic plates
,”
J. Soc. Chem. Ind.
9
,
455
(
1890
).
Google Scholar
 
4.
L. A.
Jones
, “
Photographic sensitometry, Part II
,”
J. Soc. Mot. Pict. Eng.
17
,
695
(
1931
).
Google Scholar
 
5.
A.
Callier
,
Phot. J.
49
,
200
(
1909
).
Google Scholar
 
6.
A. M.
Koerner
 and
Clifton
Tuttle
, “
Experimental determination of photographic density
,”
J. Opt. Soc. Am.
27
,
241
(
1937
).
Google Scholar
Crossref
Search ADS
 
7.
Enoch
Karrer
, “
Use of the Ulbricht sphere in measuring reflection and transmission factors
,”
J. Opt. Soc. Am.
5
,
596
(
1921
).
Google Scholar
Crossref
Search ADS
 
8.
Parry
Moon
 and
D. P.
Severance
, “
Some tests on radiation‐mixing enclosures
,”
J. Opt. Soc. Am.
29
,
20
(
1939
).
Google Scholar
Crossref
Search ADS
 
This content is only available via PDF.
© 1940 American Institute of Physics.
1940
American Institute of Physics
You do not currently have access to this content.