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An adaptation of the thalofide cell to the measurement of photographic densities
NOTES FROM THE RESEARCH LABORATORY E A S T M A N K O D A K COMPANY.* AN A D A P T A T I O N O F T H E T H A L O F I D E CELL TO T H E MEASUREMENT OF PHOTOGRAPHIC DENSITIES¢ By A. L. Schoen.
IN photographic research, it is frequently necessary to measure low densities with great accuracy. The usual visual methods for measuring density have been found inadequate for this purpose. Tests made with thalofide cells to determine the conditions for high sensitivity and stability show that this instrument can be adapted as a physical photometer for the measurement of these densities. Changes in sensitivity with applied voltage and intensity of illumination were observed. From these data the best voltage and illumination were determined and maintained constant on the cell. Densities were determined (using the inverse square law) by moving the source of illumination to produce zero deflection in a sensitive galvanometer for each step of the sensitometric strip. Results obtained thus far indicate that this method can be used with advantage in problems involving the measurement of very low densities and small density differences and that densities as low as .oo 5 ( - 9 9 per cent. transmission) can be measured with a fair degree of certainty. S I Z E - F R E Q U E N C Y D I S T R I B U T I O N O F GRAINS O F S I L V E R H A L I D E I N P H O T O G R A P H I C E M U L S I O N S AND ITS R E L A T I O N TO S E N S I T O M E T R I C C H A R A C T E R I S T I C S . V.mSYSTEMATIC CORRELATION? By E. P. Wightman, S. E. Sheppard, and A. P. H. Trivelli.
A SERIES Of photographic emulsions has been prepared of which a correlation between the grain and sensitometric characteristics shows an apparently close relationship. These emulsions are strictly comparable because practically all the factors in their preparation were under control, only one being varied so as to progres* Communicated by the Director. 1Communication No. I7I from the Research Laboratory of the Eastman Kodak Company and published in J. Opt. Soc. Amer., June, I923, p. 483. Communication No. I72 from the Research Laboratory of the Eastman Kodak Company and published in ]. Phys. Chem., May, I923, p. 466. 25I
IN photographic research, it is frequently necessary to measure low densities with great accuracy. The usual visual methods for measuring density have been found inadequate for this purpose. Tests made with thalofide cells to determine the conditions for high sensitivity and stability show that this instrument can be adapted as a physical photometer for the measurement of these densities. Changes in sensitivity with applied voltage and intensity of illumination were observed. From these data the best voltage and illumination were determined and maintained constant on the cell. Densities were determined (using the inverse square law) by moving the source of illumination to produce zero deflection in a sensitive galvanometer for each step of the sensitometric strip. Results obtained thus far indicate that this method can be used with advantage in problems involving the measurement of very low densities and small density differences and that densities as low as .oo 5 ( - 9 9 per cent. transmission) can be measured with a fair degree of certainty. S I Z E - F R E Q U E N C Y D I S T R I B U T I O N O F GRAINS O F S I L V E R H A L I D E I N P H O T O G R A P H I C E M U L S I O N S AND ITS R E L A T I O N TO S E N S I T O M E T R I C C H A R A C T E R I S T I C S . V.mSYSTEMATIC CORRELATION? By E. P. Wightman, S. E. Sheppard, and A. P. H. Trivelli.
A SERIES Of photographic emulsions has been prepared of which a correlation between the grain and sensitometric characteristics shows an apparently close relationship. These emulsions are strictly comparable because practically all the factors in their preparation were under control, only one being varied so as to progres* Communicated by the Director. 1Communication No. I7I from the Research Laboratory of the Eastman Kodak Company and published in J. Opt. Soc. Amer., June, I923, p. 483. Communication No. I72 from the Research Laboratory of the Eastman Kodak Company and published in ]. Phys. Chem., May, I923, p. 466. 25I