The Film Renter and Moving Picture News (Sep-Oct 1922)

Oct. 7, 1922. eee ee nee en nen en THE FILM RENTER & MOVING PICTURE NEWS (Technical Supplement). 79: Kinematography in Natural Colours. Its Pro gress and Ultimate Success ——No. 11. By OTTO PFENNINGER. | HAVE spoken of a photographic film being exposed to colour light, but an ordinary photographie film is not affected by red light that passes through your orange red lightfilter, which you use as a protection in your dark room. We have therefore to use a specially prepared film, a film that sees green, yellow, orange, and red, and not only violet and blue, as the so-called ordinary film does. It was Professor W. Vogel, of Berlin, who discovered in 1884 that certain aniline dyes iad the property of imparting xsensitiveness in a Bromsilver film when exposed to colour rays. The proper impulse to colour kinematography came with the year 1902, when Dr. Koenig, of the colour works at Hécehst, A/M., introduced the Orthochrom commercially. A year or two later Pinachrom followed, then Cyanol and Verdol. Cyanol alone or in combination with the others is the best possible sensitiser for this class of colour work. Orthochrom gives an exposure up to about 630, Pinachrom to 645, Verdol to 645, Cyanol to 670. I like a combination of the last two. Cyanol does not vive a very good colour rendering in the blue green; which defect is reduced sreatly if Verdol is added to the colour or sensitising bath. Verdol is similar to Pinachrom, but gives a better colour rendering in the blue green near 500. Similar English colours are Sensitol Red and Sensitol Green, their advantage lies in that, that they cost about double, nor can you get the colours through a dealer. THE STOCK SOLUTIONS for sensitising dyes are now ‘always taken as one pro mille, one gramme of dye in one litre of pure alcohol. The dyes that come here into question are not water soluble, therefore alcohol has to be added to the sensitising bath to such an amount as to make sure that the colour is not precipitated out of the water bath. A water bath, however, is necessary to bring the colour into contact with the silver compound by means of the absorption by the gelatine. A typical sensitising bath is : Cyanol Stock .......:ccccceeeeceseeeseeeeeee 5 ees, Verdol Stock .......ccccccecceeeccertereeeeees 10, Alcohol, pure .....ccccccceceesceeeeseeeeenes ” Water Dist. .. e Carbonate .......cccccceseceeceeeeeeeeeeeeeens 7. The carbonate is a 10 per cent. stock solution of carbonate of potassium. The latter addition is not absolutely necessary, but assures an alcalin bath. The. slightest trace of acidity is detrimental in the process of sensitising. When the sensitising bath is ready the Bromsilver film is immersed for three to four minutes, is then withdrawn and dried. For the sensitising operation, as well as for the drying process, which should be complete in four to six hours, absolutely no light is permissible. The action of the ordinary red dark room light on a film colour sensitised is the same as a good daylight. Google ee ee en en nena The temperature for all operations in’ preparing a colour sensitive film is 18 degrees Centigrade. A temperature over 20 is too near the melting point of wet gelatine; if the temperature is too low no regular work can be done. | All your workrooms must be of equal temperature, as free as possible of moisture and dust. LIGHTFILTERS have to be used when making exposures on colour sensitive filins. They are best bought from a respeetable firm, but you can make them yourself, and if you feel you want to know more about the matter a textbook like ‘ Byepaths to Colour Photography (Penrose and Co., Farrington Strect, F.C.1.) will be of use to you. The office of a lightfilter is to eliminate light rays which are not wanted, and pass only such light rays as will, with a colour sensitive film, give vou a desired and correct exposure on the sensitive surface, forming what is called a negative colour record, One such record has to be black approximately from 400 to 521 and 650 to 700, obtained with the violet filter. The second record must be covered from 450 to 600 with the help of the erecn filter, and the third record being exposed from 575 to 650 by means of the orange red filter. If you study the spectrum you will better understand the requirements. For the addition synthesis the same filters have to be used, the projection is simply a reversal of the light action, superposing the three different positive colour records on the screen, never as colour transparencies. For the subtraction or printing method, the colour missing, the transparent parts of the negative, have to be used. Such printing has to be superposed on one transparency or print, and is projected as such like un ordinary transparency. OPTICAL AND MECHANICAL PROCESS. You now know what the primaries are, and what is required of the film and the filter, and we must follow up the information as to the optical and mechanical means employed. You may take it that Brighton is the birthplace of kinematography in colours, St. Ann’s Well, a Gardenhouse having a tower, still standing at the entrance to the Park at the south-eastern eorner, houred the first investigators of eolour kinematography, the first to show that they understood the requirements of photography in colours as applied to the cinema, The outeome of their investigations is laid down in the English Patent 6202 of the year 1899. The claimants are F. M. Lee, of Walton-on-Thames, and F. R. Turner, of Hounslow, T never heard that they had any success. Primarily they laboured under the disadvantage of having no rapid colour sensitisers. Their investigation in that direction was about four years too carly, The then known colour sensitisers of any value were the Cyanius and specially the Azalin, by Dr. Vogel, of Berlin. Ortheerhom, which acts ten to twenty times quicker, was commercially introduced about 1902 only. (To be continued.)