International photographer (Jan-Dec 1935)

Four The INTERNATIONAL PHOTOGRAPHER January, 1935 makes possible exposures of 1/25 to 1/1000 second. An The facts mentioned above are rather concise but other remarkable feature of this film is that no filter is will serve as a basis for those who wish to experiment required in ordinary daylight, quite a tribute to the with developing formulas. In any event we would like progress made in the sensitizing of film. This film to hear from miniature camera photographers who have should not be confused with the Agfacolor lenticular pet fine-grain formulas with which they are getting good base film which requires a special filter, both for taking results. We would like to pass them along for the and projecting, the color in the latter case being supplied benefit of other small camera workers, by the filter. The lenticular base film merely carries a Before closing this subject it would be well to reblack and white record of the color. We may look for produce the Buffered Borax formula for the benefit of ward to having the new film introduced into this coun those photographers who may not be acquainted with it. try about the first of the year. Buffered Borax Formula The Requirements of a Fine Grain Developer: Per Elon, Metol etc. 1 Gm. 15 gr. haps the new year will inspire many to experiment with Hydroquinone ' 2 5 Gm 38 gr! new developing formulas. With this thought in mind Sodium Sulphite 50 Gm. U/A oz. I am listing below the requirements of a hne gram de Borax 1 Gm 15 gr veI°Per: Boric Acid 7 Gm' 105 gr". 1. Its alkaline content should be low: The greater Water, to make 500 c.c. 16 oz. the alkalinity of the developer the more will the emul gtir constantly when adding the sulphite and borax sion swell allowing the deve oper to diffuse through it tQ preyent the chemicals from caking_ The borax should more readily and alkalinity also affects the speed of de be kept in wfiU stoppered containers to prevent it from velopment. If the alkaline content is high the develop becoming dehydrated. This would result in a higher alka ing action will proceed at a great rate, the grains easily lmity gince h the aboye formula the hydrated form is rupturing the swollen and tender gelatin support uniting tQ be usedi whJch contains ten molecules of water per to form clumps of reduced silver grains, resulting in molecule of borax. Higher alkalinity would mean that coarse grain. High alkalinity makes the emulsion more nQt as fine a grain wouU be produced. receptive to the developer and increases the rate of Jbouf Exposure A?aln: It has oft been repeated but action. , , • it is worth while again emphasizing the fact that over 2. The potential of the developing agent should be exposure ,-, detrimentaj to fine-grain results. When an low: The potential of the deve oping agent is its ability overexposed, negative is developed the action proceeds to attack the exposed silver halide grain. The slower ^ a great the rapidly reduced silyer grains ruptur. a developer performs this action the finer is the grain ing theJr kt;ne support and uniting tQ form dumps it produces. Below is a list of the reduction potentials of grains_ h fe thege d of grains which cause of the more common developing agents as outlined by graininess. Despite this important fact you will find a Dr. V. B. Sease. You will notice that paraphenylene great number of photographers stiH gueSsing at exposure, diamine heads this list : or referring to a tablej wb;cb ;s t00 general in character Paraphenylene-diamine ---- 0.3 t0 produce the best results. Hydroquinone 1.0 Many wiU gtate that thdr metbods are yielding pic *jr ycin 1.0 tures. True! The modern emulsion has extreme lati Metol Khodol, etc. ■ 20.0 tude yQU can gjye seven or more exposures varying " relatively greatly in time, and each negative will be 3. The concentration of sodium sulphite: Whereas capable of yielding a picture, but will naturally vary in this chemical formerly just played the role of a pre density. Suppose we select two negatives from this group, servative, preventing the oxidation of the developer, it one which has been correctly exposed, and the other havis now employed in high concentration in fine-grain de jng received about a three or four times overexposure, velopers because of its solvent action on the silver salt Having been developed in the same solution for the in the emulsion. While the film is being developed the same time the overexposed negative will be comparativesodium sulphite dissolves away a portion of the silver \y denser, and it is a fact that if a print of constant halide grain with the result that finer grain is pro density is made from negatives of increasing density, the duced. graininess of the print increases as the density of the These are the three main factors dictating the ability negative increases. You can try this yourself by taking of a developing solution to produce fine-grain negatives. two negatives such as described, blowing them up to a By the addition of a restrainer such as the boric acid very large size in the enlarger, and making prints of equal in the Buffered Borax formula, the developer will pro density on a glossy paper. The results will tell the story duce a finer grain. Perhaps we should explain the mean of how graininess is augmented by overexposure, ing of a buffer. Overexposure also affects sharpness. An emulsion By combining a weak acid and its sodium salt a consists of many layers of silver grains. Suppose that "buffer solution" is obtained, so-called because it sta to reproduce the detail in a shadow it is necessary to bilizes the alkalinity of the developer. If the ordinary give an exposure that will result in one layer of silver well-known D-76 formula is allowed to stand for some grains to be deposited in the subsequent development, time it increases in alkalinity, consequently in develop Instead the negative is overexposed, so that about four ing speed, with the result that a coarser grain is pro or five layers of silver grains are deposited. The reduced in the film developed in it. This is overcome by suit is the same as looking through a fine mesh matethe addition of boric acid to this formula (seven times rial. By adding successive layers of the material definithe amount of borax) producing a "buffer solution" tion will suffer. which has the ability to resist chemical agencies that tend The answer to the entire question is to use a reliable to increase or decrease the alkalinity of the developing exposure meter, either of the "extinction type," or the solution. The Buffered Borax formula can be made up new photoelectric cell meters, as the Photoscop or the and stored, in normal dilution, for as much as two months Weston Meter. The accuracy of the latter meters canwithout any perceptible change in its qualities. The ad not be doubted. They work on the principle of condition of the boric acid prolongs the development, there verting light energy into electrical energy. The Photofore the sulphite is given a longer time to act on the scop meter requires no calculations, giving direct readsilver halide grain, producing finer grained negatives. ings, and also effectively reduces the angle of the light Please mention The International Photographer when corresponding with advertisers.