International photographer (Jan-Dec 1934)

Four The INTERNATIONAL PHOTOGRAPHER February, 1934 Miniature Cameras and f^m\ Photography v« * * ENERALLY, in classifying films according to grain, orthochromatic is at the head of the list, panchromatic follows, and supersenitive panchromatic emulsions display the coarsest grain. There are exceptions as in the case of Micropan and Panatomic films. Here are two excellent films exhihiting a grain which is finer than that obtained with many orthochromatic emulsions, and they also possess the additional advantage of complete color sensitivity. They are, however, relatively slow in speed, Panatomic film having the same speed as ordinary N. C. Kodak film, and Micropan being about J4 as fast as an ordinary panchromatic film. This emulsion was formerly known as Quarterspeed Panchromatic, its new name most likely having been adopted through the fact that it is extensively employed in photomicrography. Micropan film is contrasty, and possesses a relatively thin emulsion. In order to avoid excessive contrast it is recommended that it be developed for only % of the normal time. It was mentioned before that Panatomic film has about the same sensitivity as ordinary N. C. film. This is a difficult comparison to make. During the middle of the day this may hold true. In the early morning, or late afternoon, when daylight exhibits large quantities of red and yellow, the speed of N. C. film will be far below that of Panatomic, for the latter is fully color sensitive whereas N. C. film is blind to yellow and red. Similarly with the use of artificial light N. C. film cannot hope to compare with Panatomic in speed. The chromatic sensitivity of the latter is similar to that of supersensitive panchromatic film. The filter factors for both of these emulsions are therefore similar. Filter factors for Panatomic film are as follows: Filter Kl Kodak Color Filter. K2 G XI X2 5.0 Because of the extreme contrast it produces Micropan film is recommended for photomicrography, and copy work. When desired to use it for ordinary purposes a soft developer should be employed ; its slow speed will however limit its employment in general photography. This film is only supplied for the cine type camera. The use of a hardening bath : The principles upon which miniature photography is based demand the utmost care of the negative. A small scratch which may be barely visible on the tiny negative will reveal itself to be a serious marring factor when the negative is enlarged. During its employment in the production of prints the negative is unavoidably handled to a certain extent, and is thereby subject to suffer slight scratches. In order to prohibit such detriments it will be necessary to toughen the film while it is being processed. I have found an excellent hardener for the emulsion to be the chrome hardening bath recommended by Eastman for the processing of films under tropical conditions. The formula for this bath is as follows: Potassium chrome alum 30 grams Water to make 1 liter Daylight T unqsten 1.5 1.2 1.8 1.4 2.0 1.5 2.5 2.0 5.0 By Augustus Wolfman of the above formula into avoirdupois weights is — chrome alum one ounce and water to make one quart. After the film has been developed it is rinsed and then placed in the above hardening bath for at least three minutes. Longer immersion will do no harm. It is necessary to agitate the film for about 45 seconds when first immersed in this bath, to prevent the formation of blisters and a sludge of chromium hydroxide. From the hardening bath the film is transferred to the fixing solution, the rest of the processing concluded in the usual fashion. Potassium chrome alum solutions do not keep very well, so that the hardening bath should be made up just before use. Although it can be used for a number of films, it is advisable to prepare a fresh solution for each film, for as the concentration of the developer brought over by the films increases, the bath rapidly loses it hardening properties. Films treated with this hardener should be carefully wiped after washing and before drying, to remove any chromium scum present. The latter if not removed, will cause a stain that will resist attempts to remove it. On leaving the chrome alum bath the film will be so hardened that the gelatin will not dissolve off in boiling water. This is quite a degree of hardening, for ordinarily the gelatin will run off the film when it is placed in hot water. Boiling water will clean the gelatin off an unhardened negative with lightening rapidity. There is also a commercial process available known as the Scratch-Proof Method, which hardens the gelatin to such an extent that determined efforts to scratch it will fail. Photographers who possess valuable miniature films which are frequently called upon to produce prints should investigate this process. The Vest Pocket Dolly The Dolly Camera: Here is a fine little camera that is supplied in models to suit many needs and purses. The Dolly is not a new addition to the miniature camera field. It appeared just as miniature photography was springing into popularity and is really one of the pioneers that helped the miniature rise to the popularity it now enjoys. The Dolly is supplied in two models, a miniature size which takes 16 pictures each measuring 1 3/16 by 1 9/16 inches on a roll of vest pocket film. The second model takes the full vest pocket size picture. Various lens and shutter equipment are supplied, from a camera having a Certar f :4.5 lens and Vario shutter, to one equipped with a Compur shutter, and a Zeiss Tessar f :3.5 or Ultra High For those not possessing metric weights, a conversion Please mention The International Photographer when corresponding with advertisers