Business screen magazine (1944)

rrie.Tiures. The condition will van fioin lie setup to another and no one sysieni . in be employed to remedy all cases. ■ Mdencies in ihe light reaching ihe t film tan be corrected by introchic _ color filter solutions prepared by ■man Kodak Company .= ' \i the lower powers, up to lOOX or and when photographing specimens • Mil as those illustrated here, it is .ioiiblful if such color compensation M tually necessary. No color corapensa :i was found necessary when the origi • uf the accompanying illustrations I made. Exposure Methods have been described wherephotoelectric exposure meters or ;.il photometers are used to deteriiinc the correct exposure time for the liiir films. Such devices, if carefuUv ! are convenient and will give ac* lie determinations, providing the lity of light and illumination con'■in in general have been correctly i-«ted for the particular color film. tie event some form of photometer uinnut be used, the correct exposure lime can be determined photographically, by first making trial exposures on black and white materials and then calculating the exposure time for the color film from the known speeds of the two materials. Theoretical]) . the black and white material used for making such exposure tests should be of the reversal type. However, in determining the exposure for the originals of the accompanying illustrations, ordinary negative materials were employed. The illustrations presented here were selected from a series of color photomicrographs including stained sections as well as chemical crystals in polarized light. Type B Kodachrome and the professional Ansco Color Sheet films were both used in making tlie complete series. Lacking other means of exposure determination, ii was decided to try tlie exposure test method with black and white negative material, choosing the exposure giving a gt»od range of tone when the negative was developed normallv. The negative material used for making Ihe cx|xisure tests included both Eastman Panatomic X and Defender Fine Grain Panchromatic Films. The Wratlen X-I filter was placed in the illuminating l>eam when the trial exposures were made. The negatives were processed in Kodak formula DK 60a developer for 4 minutes at 200C. Previous to exposing each color film an exposure lest strip was made on the negative material. From this test strip the exposure judged to be correct was chosen. A full»i/e negative vvas then cxposcil to provide a better over all judgment of the exposure. The ratio of the recommendc-d Weston speed nunil>ers for the negative and color material was then applied to determine the exposure for the color film. At the ouiM.-t three color films were exp<jsed i>er s[x?cimen, using the estimated time and exposures 25 to 50 per cent shorter and longer. The color films were returned to the manufacturer for processing. The finished transparencies were compared with tJie original specimen projected onto the camera ground glass. when possible to do so. It was found that the exposures determined by the method described produced satisfactory results and the practice of including the longer and shorter exposures was discontinued. It should not be concluded that this method of e.xposure determination is presented as an approved and certain procedure. -\s stated earlier, the method is contrar\ to iheor\'. However, the results obtained were entirelv satisfactory and the method apparently is applicable in the event approved methods cannot lie used. The photomicrographs presented here were taken on the large Bausch jl: Lomb PholomicTographic Equipment. The originals were made on 5 .x 7 film. No color compensation was employed. .\ 78C filter was used to correct the color temperature of the Ribbon filament lamp to 3200° K. Polaroid discs were used as the polarizing elements. One at the illuminator, directly in front of the \Vratten 78C filler, acted as the polarizer and the other above the eyepiece rimmediatelv behind the Micro Tessar in the case of the Tartaric Acid illustration) . as the analyzer. A first order red retardation plate was held between the anaIvzer and the microscope eyepiece. The polarizing elements were rotated to produce the most vivid colors. The specimens were all prepared without cover glasses. In the case of specimens mounted with cover glasses, it is advisable to use colorless mounting medium if possible. Furthermore, when an oil immersion objective must be used, a colorless immersion oil is recommended. The use of these materials will help to reduce the problem of color compensation. BIBLIOGRAPHY 1. A Color Temper,\ti.re Meter— E. M. Lovvry and K. S. Weaver— JI. of Soc. Motion Pict. Eng.-Vol. 32— (1939) . 2. Kodachrome PiiOTOMicRCK.R-\PHv of Stained SLmEs— JI. of the Biological Photographic Association— Vol. XII, No. 4, June. 1944. (Communication No. 954 from the Eastman Kodak Research Laboratories. Rochester, N.Y.) 3. Mktai-Locraph^ in C'.oi or — R, P. l^vcland— A.S. T. M. niiUcIin No. 128, Ntay. 1941. (Communication No. 964 from the Kodak Research Laboratories.) 4. I'llOTOMICROCRAPHV IN THEORY AND PR.AcriCE-CharIcs P. Shillaber, New York. John Wiley and Sons (1944). 5. PiioTOMicRDc.R.M'Hv— (I4ih Edition— 1944) .\ Publication of the Eastman KtKlak Co., Rochester, N. Y. G. F\fLTS IN PlIOIOMItniOCRAPHYJ. V. Bntterfield— The Educational Focus -Vol. X. No. I -Spring, 1939Ballsch .<: Lonih Optical Co,— JI. of the Biological Photographic Association—Vol. 10— June. 1942. ATLAS Educational Film Co. SINCE 1913 PRODUCERS OF INDUSTRIAL AND EDUCATIONAL FILMS CREATORS OF MOTION PICTURES & SLIDEFILMS 1111 South Bonlevard • Oak Park, lUinois • AUStin 8620 M i EVERYTHING IN PROJECTION 35nun Projection 16mm Mazda Projection 8mm Projection 2x2 Slicie Projection Sound Slide Projection Turntable Furnished 16mm Arc Projection 1 6mm Silent Projection Standard Slide Projection Film Roll Projection Opacfue Projection Microphone Furnished P. A. Systems set up Thirteen offices ready to serve you! 28 34 E. 8th St., Chicago, Illinois (Home Office) 2024 Main Si.. Dallas 1, Texas 714 18lhSl.. Denver 2. Colorado 926 Mr(..f .><l.. Kan^a^■ Cilv 6. Mi>-iiiiri 2108 W. Tlh Si,. Los .^nReie,. 5. ('.aliffirnia 18 So. Third Si.. Mtniphi^ 3, Tennessee 1.S2 So, Miami A\e,. Miami 36. Florida 826 Baronne Si,. 2nd Floor, New (Irleans 1,3. Louisiana 91.1 S, W, lOlh Ave Portland 5. Oregon 108 W. Sill St.. C.hallanooKa 2. Tennt^see 219 l:. Main St.. Hii'lininn.l 19. \ irginia ,i2 .Vuburn .Vve., N. E,. .\llanla, (■e<irgia IScrlruiii W illoii^lil>> Pictiircs. Inc. Suite 600. UiOO |{r<>uil»uv. >,« York Citv 19. >rw York NUMBER FOUR • VOLUME SEVEN • 1946 51