US1949911A - Photographic developer - Google Patents

Description

Patented 6, 1934 UNITED STA PHOTOGRAPHIO DEVELOPER Fritz J. Hepner, Potsdam, Germany No Drawing. Application November 8, 1927, Serial No. 232,002. In Germany December 15,

2 Claims.

Y tion that in the developing of photographic negatives bromine is separated which is dissolved in the developing liquid and in this condition produces a retarding action upon the developing procedure. If the negative is allowed to remain 1 in a reclining position or as horizontally as possible and without agitation in a highly diluted developing solution for a sufficient length of time, comparatively more bromine will be eliminated at the majority of the portions exposed to the light than at those portions of the negative which have been less subjected to the action of the light. These comparatively larger quantities of the bromine separated out in the more lighted portions and which are deposited there, have a :5 retarding action, while the portion upon which the light has acted less, will be developed and finished more quickly, relatively speaking, be-

cause smaller amounts of bromine will be liberated at these places. .0 Now it has been ascertained that by using'developers of the, usual composition disturbing clouds or veils are liable to be formed with this kind of long-time-horizontal development, and fluctuations of temperature are of great influence, and the degree of dilution is of importance,

and can only 'diflicultly be determined in advance, particularly where there is lack of distilled water. Now it results from my investigations and experiments that these difflculties may 40 be overcome and that it is possible to produce negatives exhibiting a harmony of shades such as has been impossible to produce heretofore by any other procedure according to the previousart, particularly in a simple and easy manner, 4.5 by making use of developers of any usual com-v position, but containing no caustic alkali, salts or other additions containing or forming caustic alkali by hydrolysis or other decomposition procedures, in combination with the long-time-horizontal developing process and in concentrations that are much lower than those used for the customary tank or stand development. It has been shown that withv such developers the most delicate degrees of shades contained in the nega- 56 tive may be brought'out, and the positives are free from halos and clouds and with the entire outlines of the picturein shadow parts. This method is adaptable to-all kinds of pictures with absolute reliability, and all sources of defects otherwise occurring in the developing of photo- Q0 graphic negatives are thereby avoided. The new process has the further advantage that it suppresses or at least does not emphasize the exposure of the emulsion particles near the surface of the emulsion. It is well known that these emulsion regions receive the full exposure with blue light, which light however is absorbed by the yellowish emulsion as it penetrates to deeper emulsion strata. Hence, the new process obviates in many cases theuse of yellow filter, during the exposure of the negative, suppressing the blue light rays. The time required for the developing process may vary between about 4 and about 14 hours, and it becomes possible in con sequence thereof to leave the plates to be developed in the liquid without special care, and to submit them to the fixing treatment, when the operator is at leisure.

Examples Distilled water cc.

Sodium-sulfite 15 grs.

3 grs, Potassium-bromide Distilled water -400 cc.

Metol (qmgfi gznzso, (methyl amido-phenol-sulphuric acid) 6 grs. Sodium-sulfite 60 gr's. Potassium-bromide 0.6 grs.

The figures given above show the contents of a concentrated or commercial developing solution. For the practical use this developer should be diluted, e. g. in relation of 1 cubic centimeter to 25 cubic centimeters water.

.Development of photographic silver haloid emulsions in substantially horizontal position, in undisturbed, alkali free-and highly diluted developer solutions, as above described, has the following effects. The highly diluted alkali free developer quickly penetrates the emulsion, upon which it has no initial tanning action, so that development begins uniformly throughout the emulsion. When the development progresses, bromine is gradually set free with the above described beneficial efiect upon the high light portions. After some time the developer-begins to sion, an approximately horizontal position being sufiicient.

It should, of course, be understood that the invention is not restricted to these specific exempliflcations, but that it may include other embodiments both as regards material and proportions, except as otherwise stated in the appended claims.

1. Photographic developer for long-time-horizontal developing, comprising a solution of substantially sixty grams sodium-sulflte, substantially six grams metol and six tenths gram of potassium-bromide in substantially four hundred cubic centimeters of water, and tree from caustic alkaline additions.

2. A method for developing photographic silver haloid emulsions which comprises placing the emulsion support with the emulsion facing upwardly and approximately horizontal into an aqueous solution of metol or glycin developing agent at a concentration of less than approximately one quarter of one per cent, and not less than approximately one sixteenth or one per cent,

containing water soluble sulfite but being substantially free from alkali, and retaining the emulsion in said solution substantially undisturbed several hours until fully developed.

. FRITZ J. HEPNER.