William 1. Jolly University of California Berkeley
Transparencies by Photographic Reversal
M o s t lecturers look upon slide-preparation as a chorc to be avoided or to be delegated to someone else. Lecturers who cannot afford to have others prepare their slides but who are amateur photographers can prepare black-and-white transparencies by a simple reversal process using ordinary camera films and readily available chemicals. Exposure
Transparencies made from 35-mm film are particularly convenient because they may be economically mounted in simple cardboard mounts. The resulting 2 by 2-in. slides are very light-weight and essentially unbreakable. The Eastmau Kodak Company recommends the use of Panatomic-X 35-mm fdm for such purposes.' ASA exposure indexes of 80 and 64 (for daylight and tungsten, respectively) should be used. Roll films of larger format (such as 620 size) yield transparencies which may be mounted between 3l/& by 4-in. glass plates. Slides of this size will fit practically all lecture-hall projectors. The slide area which is not covered by the transparency should be masked with opaque paper or tape such that the side of the mask facing the projection lamp is white. An exposure index about 1.5 or 2 times the fdm manufacturer's recommended index should be used. Thus the author has obtained satidactory transparencies using the following roll films and exposure indexes: Kodak Verichrome Pan, E.I. = 160; Ansco AU-Weather Pan, E.I. = 125; Kodak Tri-X Pan, E.I. = 300; Perutz Peromnia 21, E.I. = 160. It should be pointed out that particular camera-projector combinations may require revision of these exposure indexes up or down by as much as a factor of two. When copying line drawings, exposures may be estimated by substituting a white sheet of paper for the drawing and by reading the reflected light with alightmeter, using an exposure index of three-quarters the value recommended above. Processing
For normal, continuous-tone transparencies, the process outlined in Table 1 is recommended. Transparencies made from line drawings, etc., have insnffcient contrast when processed in this manner. I n See Kodak Publication No. S 8 , "Photographic Production of Slides and Filmstri~s"and Kodak Pam~hletNo. F-19. "Blaokand-White ~rrtnspareneieswith ~ o d a k 'panatomic-X' Film in Magmines."
order to increase the contrast of such transparencies, the process should be modified as follows. The first development should be carried out for 21/2-3 minutes using Kodak D-8 developer. The redevelopment should be carried out for six minutes with the used D-8 developer to every liter of which 73 ml of 2 wt. Ojo hydrazine sulfate has been added. Both processes should be carried out in a tank and (until the final rinse) in total darkness. Table 1.
Processing of Continvous-Tone Transparencies
Step Fimt developmen1
Solution KodakD-19 to everv liter of which 20 ml of 10 wt O/, sodium thiocyenate solution bas been added.
Wash Bleach
Running water 1 wt yopotassium dichromate and 1 vol % cane. sulfuric arid. Water 10 wt %'nsodium
Wash Clear
Temp. Time 20' Panatomic-X (35 mm) and Peromnia 21, (roll film)-8 mm. Verichrome Pan and AllWeather Pan (roll filmsl-6 min. ~ r i - xPan (roll film)-9 mi'n 18-22' 2 min 18-22' 3 min
18-22' 18-22'
1 min 2min
Redevelop ment
Wash Fixing and bardening Wash
20 w t yi sodium hydroxide and 75 mlof2wtX hydraeine GIfate has been added. Water 18-22' Any good fixer18-22' hardener. Running water
18-22'
lmin 5 min 10 min
I t will be noted that, in the above reversal processes, the second development is not preceded by the usual flash exposure. This omission is made possible by the use of second developers containing the fogging agent hydrazine. Hydrazine sulfate is a readily available chemical, and the preparation of the redevelopers by the addition of hydrazine sulfate to the already-used first developers is very simple. Both of these advantages are lacking in a published process2which involves a second developer containing both sodium dithionite and 24hiobarbituric acid. Kodak Pamphlet No. J-6, "Formulas and Processing Kodak Direct Positive Panchromatic Film 35 mm."
Volume 39, Number 2, Februory 1962
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