. Transactions of the Society of Motion Picture Engineers (1921) . at a certain temperature, he knows that with thedeveloping formula given a suitable y or contrast will be obtained,that will give the best average rendering of the object photographed. Figs. 13 and 14 show typical factory charts of negative andpositive film. The negative has a speed of 243, comparatively lowcontrast, yl being .36 and y2 being .66 obtained in 23^^ and 5 minutesdevelopment, y oo is The curves show the quality necessaryfor a negative emulsion, a long scale capable of faithfully render- 148 Rycor riimGl-rv=,-
. Transactions of the Society of Motion Picture Engineers (1921) . at a certain temperature, he knows that with thedeveloping formula given a suitable y or contrast will be obtained,that will give the best average rendering of the object photographed. Figs. 13 and 14 show typical factory charts of negative andpositive film. The negative has a speed of 243, comparatively lowcontrast, yl being .36 and y2 being .66 obtained in 23^^ and 5 minutesdevelopment, y oo is The curves show the quality necessaryfor a negative emulsion, a long scale capable of faithfully render- 148 Rycor riimGl-rv=,- Ml» at . ti . Incnij , i4 Speed ^H^. Doel«p ,cn,r,no, 3t ,,.. „^„ si„ ^0^.0 . 1 ) i Dale f/l^l-iA ( V, ^59/ ^1 ■ : / • — ^ / y / y ^^ ^ ^ // ^ y\^ / 1^ /■ ^ A # i==\_ . Fig. 13—Typical Factory Chart for Negative Film. PiMt « J9f»eloper>rs H^..,^ C ilMCIlAMTOM WORKS B.,.l»pcd ,...^. Ifitlor.^,// Ditc .. £,,.„„J?.. ..iK«-!Vv?vy<. ►,. Fig. 14—Typical Factory Chart for Positive Film. ing a long range of tones and a long straight-line portion indicativeof latitude in exposure. The longer the straight line portion thegreater the latitude, that is to say greater errors may be made injudging exposure and a good negative still obtained. The positiveemulsion shows the degree of contrast necessary for the produc-tion of a rich positive of good projection value. Some other uses for this system of measuring emulsion char-acter are testing of developing solutions, the action of intensifiersor reducers. The various results obtained with difTferent developers,tank solutions, temperature of development or time of develop-ment, can be shown graphically, and the instructions issued with thefilm are arrived at after careful testing in this manner. The photo-graphic value of light sources can be very effectively measured andtheir relative actinic power plotted. Apart from the determination of the speed
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