Colour Photography 
THREE-CoLouR FiLtTers.—The quantity of dyes is given 
in grams per square meter and grains per 1000 square inches. 
An 8 per cent solution of gelatine should be prepared (see 
Orthochromatics ). 
Red filter: 
Rose Bengal L25e 12.53 er. 
Tartrazine 20¢ 19.9 gr. 
Green filter: 
Naphthol green 04g 3.98 gr. 
Patent blue 0.2 ¢g 1.99 gr. 
Tartrazine 10¢ 9.95 gr. 
Blue-violet filter : 
Acid rhodamine 0.6 g 5.97 gr. 
Toluidine blue 18¢ 17.91 gr. 
The usual quantity of dyed gelatine is 700 ccm per qm (15 oz., 
435 min., per 1000 sq. in.). 
ADDITIVE FILTERS.—These are used for additive projection 
or with the photochromoscope. The gelatine should be pre- 
pared as previously described. 
Blue-violet filter : 
Crystal violet 1.38 g 2.63 gr. 
Methylene blue 0.46 g 0.876 gr. 
A few drops of glacial acetic acid should be used to dissolve 
the above. Allow the same quantity of dyed gelatine to the 
same area. 
Green filter: 
Tartrazine 0.533 5.3 ote 
Patent blue 0.089 g 0.883 gr. 
Naphthol green 0.178 g 1.76 gr. 
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