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Comparison of some developers for sensitometric standardization
434
EASTMAN
KODAK
COMPANY
NOTES.
[J. 17. I.
followed in the case of thioanilides and iminazoles by firmer attachment of the silver ion to nitrogen, whereby these silver ions become resistant to reduction or sulfiding, so that growth of the isolated speck is inhibited. In the case of phenazine dyes, the electro-adsorption is not followed by firmer union, but oxidative attack of the speck by the dye is facilitated. COMPARISON
OF SOME DEVELOPERS FOR STANDARDIZATION 2
SENSITOMETRIC
S. E. Sheppard and A. P. H . TriveIli
THE question of a standard developer for sensitometry was discussed at the Seventh International Congress of Photography. Since p-aminophenol has several advantages over pyro, S. E. Sheppard proposed that it be taken as a standard developer. This proposal was adopted. The formula examined and approved is: p-Aminophenol hydrochloride .................. S o d i u m sulfite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sodium carbonate ............................ W a t e r to . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.25 5o.oo 50.00 I
grams grams grams liter
Sensitometric comparison was made on three grades of emulsion, slow, medium, and rapid, with the proposed p.-a.-p., pyro soda, and elon hydroquinone developers. It was found that the p.-a.-p, gave equal speed, equal gammas for less fog, and somewhat lower development rate. A comparative study was made of the microscopy of the silver halide grain on development in the three developers. The transformation of the silver halide grain to silver shows three principal stages, morphologically. These are nucleation, process formation, and deformation, p-Aminophenol was found to give less spontaneous nucleation than the other reducers, agreeing with slighter fogging power. The photometric equivalents of the silver images produced by the developers studied were much the same at equal degrees of development. C o m m u n i c a t i o n No. 347 f r o m t h e K o d a k R e s e a r c h L a b o r a t o r i e s a n d p u b lished in Proc. Seventh International Congress Phot., 174 (1929).
EASTMAN
KODAK
COMPANY
NOTES.
[J. 17. I.
followed in the case of thioanilides and iminazoles by firmer attachment of the silver ion to nitrogen, whereby these silver ions become resistant to reduction or sulfiding, so that growth of the isolated speck is inhibited. In the case of phenazine dyes, the electro-adsorption is not followed by firmer union, but oxidative attack of the speck by the dye is facilitated. COMPARISON
OF SOME DEVELOPERS FOR STANDARDIZATION 2
SENSITOMETRIC
S. E. Sheppard and A. P. H . TriveIli
THE question of a standard developer for sensitometry was discussed at the Seventh International Congress of Photography. Since p-aminophenol has several advantages over pyro, S. E. Sheppard proposed that it be taken as a standard developer. This proposal was adopted. The formula examined and approved is: p-Aminophenol hydrochloride .................. S o d i u m sulfite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sodium carbonate ............................ W a t e r to . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
7.25 5o.oo 50.00 I
grams grams grams liter
Sensitometric comparison was made on three grades of emulsion, slow, medium, and rapid, with the proposed p.-a.-p., pyro soda, and elon hydroquinone developers. It was found that the p.-a.-p, gave equal speed, equal gammas for less fog, and somewhat lower development rate. A comparative study was made of the microscopy of the silver halide grain on development in the three developers. The transformation of the silver halide grain to silver shows three principal stages, morphologically. These are nucleation, process formation, and deformation, p-Aminophenol was found to give less spontaneous nucleation than the other reducers, agreeing with slighter fogging power. The photometric equivalents of the silver images produced by the developers studied were much the same at equal degrees of development. C o m m u n i c a t i o n No. 347 f r o m t h e K o d a k R e s e a r c h L a b o r a t o r i e s a n d p u b lished in Proc. Seventh International Congress Phot., 174 (1929).