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Screen-Plate Practice 517
for near objects practically cover the ground; very near objects, photographed to a relatively large scale, being considered on their merits, using the near position as a basis.
Development. — The first developer recommended by the makers of the Autochrome plates was the following:
A. Pvrogallol 30 g.
Alcohol 1000 ccs.
B. Potassium bromide 30 g.
Ammonia 150 ccs.
Distilled water 850 ccs.
For use mix A 10 parts, B 10 parts, water 100 parts. Duration of development, 2l/2 minutes at 15° C.
Subsequently"'2 the following was recommended for correcting errors in exposure and difference of temperatures. Multiply the correct time, 2 y2 minutes at 15° C, by the following factors for the given temperatures : ' 10° C. multiply bv 1.6 15° C. " " 1.0 20° C. " " 0.8 25° C. " " 0.6 For overexposure, modify the developer as follows: Degree of overexposure Developer Time of development
Sol. A 20 ccs.
4 to 8 times Sol. B 5 ccs. 6y> minutes
Water to 100 ccs.
Sol. A 20 ccs.
8 to 15 times Sol. B 3 ccs. 6J/2 minutes
Water to 100 ccs.
For underexposure, modify as follows:
Degree of underexposure Developer Time of development
Sol. \ 10 CCS.
J/i to J/2 correct Sol. B 20 ccs. 6 minutes
Water to 100 ccs. Sol. A 6 ccs.
less than y correct Sol. B 20 ccs. 6 minutes
Water to 100 ccs. For stand development the following was recommended :
Solution A 20 ccs.
Solution B 20 ccs.
Water 1 500 ccs.
This takes about half an hour and could be used for six plates.
Later'!:! a still further modification was suggested, which did away with the alcohol, and gave a solution that had less tendency to oxidize in use:
A. Pyrogallol 30 g.
Potassium bromide 30 g.
Sodium bisulfite lye 20 drops
Water to ' 1000 ccs.
B. Sodium sulfite, anhydrous 100 g.
Ammonia, sp. gr. 0.920 150 ccs.
Water to 1000 ccs.