30 PHOTOGRAPHIC FACTS AND FORMULAS 
To make the dyed gelatine, the following quantities of 
filter yellow (Hoechst) should be used (Hubl) : 
No. 1. Filter yellow 0.5¢ 4.97 gr. 
No. 2. Filter yellow 10¢ 9.94 gr. 
No. 3. Filter yellow 20¢ 19.88 gr. 
No. 4. Filter yellow 3.4¢ 33.8 gr. 
No. 5. Tartrazine 3.0¢ 29.84 gr. 
The above quantities of dye should be dissolved in 50 to 100 
ccm (384 to 768 min.) distilled water, and added to sufficient 
gelatine solution to make 700 ccm (15 oz., 435 min.) in all. 
This quantity should be coated on 1 qm or 1000 sq. in. of glass. 
The increase of exposure with these filters varies with the 
colour-sensitiveness of the plates used, but the following will 
be some guide: 
No. 1. Increase from ¥% to 2, according to plate. Can be 
used for instantaneous work and portraiture in the studio. 
No. 2. Increase from 2 to 6. Can be used for distant 
mountains and costume studies. Yellow reproduced the same 
tone as blue. 
No. 3. Increase from 6 to 8. Gives yellow much brighter 
than blue. 
No. 4. Increase from 4 to 12. Correct luminosity filter. 
No. 5. Increase from 4 to 15. Contrast filter. Reproduces 
blue like black, yellow like white. Suitable for cloud studies 
in which the sky is to be very dark, and furniture. 
Konig recommended the following quantities of filter 
yellow to the same areas as above: 
No. 1. Filter yellow 0.146 g 2.25 or. 
No. 2. Filter yellow 0.292 g 4.5 gr. 
No. 3. Filter yellow 0.594 ¢ 9.0 gr. 
No. 4. Filter yellow 1.167 g 18 gr. 
The increase in exposures should be 1.3, 1.7, 2, and 3 re- 
spectively. 
