344 



Tables 372 and 373 



TABLE 372. — Spectrum Sensitivity of Photographic Materials 



The spectrum distribution of sensitivity may be shown qualitatively by wedge spectro- 

 grams. These (see preceding page) are made with a spectrograph over whose slit is mounted 

 a wedge of neutral gray glass, the transmission of which increases logarithmically from the 

 thin to the thick end. The boundary of the exposed area outlines approximately a curve 

 which is the resultant of the spectral sensitivity function of the material and the spectral 

 distribution of energy in the radiation emitted by the source illuminating the slit of the 

 instrument. The source used is an acetylene flame operating at a color temperature of 

 236o°K. All plates had the same exposure. By the application of a correction based on the 

 spectral emission of a black body at 236o°K., an approximation to the actual spectral sen- 

 sitivity of these materials may be obtained. The neutral glass wedge, while fairly non- 

 selective in absorption for radiation of wave lengths longer than 450 m/*, increases in 

 density for radiation of wave lengths shorter than 450 m^- The apparent falling off in sen- 

 sitivity at wave lengths less than 450 myu is therefore due to excessive absorption of the 

 neutral wedge rather than to a decrease in the spectral sensitivity of the materials. (Mees, 

 Journ. Franklin Inst., 201, 525, 1926. Walters and Davis, Bur. Standards Bull., 17, 353, 

 1921.) 



Note: Photo plates for spectroscopy and astronomy. 

 753. 1931- 



Mees, Journ. Opt. Soc. Amer., 21, 



TABLE 373. — Relative Photographic Efficiency of Illuminants 



C = luminous efficiency of source (lumen/watt). E r = relative photographic efficiency 

 of source evaluated on basis of equal visual intensities, sunlight = 100%. E„ — relative 

 photographic efficiency of source evaluated on basis of equal energy consumption by the 

 source, sunlight = 100%. (Jones, Hodgson, and Huse. Trans. Ilium. Eng. Soc, 10, 963, 

 I9I5-) 



Source 



Photographic material 



Ordinary 



E r 



E e 



Orthochromatic 



Er 



Panchromatic 



Er 



Sun 



Sky 



Acetylene 



Acetylene (screened)* 



Pentane 



Mercury arc in quartz. . . . 

 Mercury arc in nultra glass 

 Mercury arc in crown glass 



Carbon arc, ordinary 



Carbon arc, white flame. . . 



Carbon arc, enclosed 



Carbon arc, "Aristo" 



Magnetite arc 



Carbon glow lamp 



Carbon glow lamp 



Tungsten (vacuum) 



Tungsten (vacuum) 



Tungsten (gas filled) 



Tungsten (gas filled) 



Tungsten (C 3 ) 



Tungsten (C 3 ) 



Mercury vapor 



150 



■7 

 .07 



•45 

 40.0 

 35-0 

 37-0 

 12.0 

 29.0 



9.0 

 12.0 

 18.0 



2.4 



3-2 



8.0 



9-9 

 16.6 

 21.6 



8.9 

 11.0 

 23.0 



100 

 181 



30 



81 



18 



600 



218 



324 

 126 



257 



175 



796 



106 



23 



25 



33 



37 



56 



64 



95 



108 



3i6 



158 

 50 

 79 

 10 



52 

 1 1 

 62 



.14 



•037 



•053 



5 



7 

 47 



100 



155 



44 



85 



28 



500 



195 



275 



112 



234 



177 



1070 



115 

 32 

 35 

 4i 

 45 

 62 

 68 

 87 

 99 



354 



.21 

 .040 

 .086 

 132 

 46 



68 

 9 

 45 

 11 

 86 



14 



•52 

 •74 



2.2 



3-0 



6.8 



9.8 



5-2 



7-3 

 54-2 



130 



52 



89 



42 



367 



165 



249 



104 



215 

 165 



744 

 82 



42 

 45 

 50 

 53 

 70 

 76 



95 

 106 



273 



100 



.24 



.042 



•13 



99 



39 



62 



8-5 



4.2 

 10 

 60 

 10 

 .68 

 •95 



2-7 



3-5 



7-7 

 11 



5-6 



7-9 

 42.0 



* Screened with Wratten No. 79 filter. 

 Smithsonian Tables 



