1912] on tlip Oaumont Sprakin;! ('incmatograpli Films. 480 



2. This sensibility must be such as to permit fourteen views ))er 

 second as a minimum to be taken. 



8. The superposition of the three views must be as perfect as 

 possible on the screen, and reproduced at the same rate at which tiic}- 

 were taken. 



To facilitate the comprehension of the projection in colours, I 

 show you on the screen — any conventional subject will do (Fig. 12) — 

 eg'., a red triani^le, a green square, and a blue circle. Below on the 

 left, the negative tilni of these figures after development, and on the 

 right side, the same series of three figures as positives. Suppose we 

 place the series of three positives behind the three objectives of the 

 Cinematograph, each one of which is provided with a coloured filter 

 through which the negative was obtained. On uncovering successively 

 the objectives we see on the screen from above downwards, each one 

 of the figures. 



The first view obtained with the red filter shows the projection 

 of the red triangle on a black ground, as the filter allows only the 

 red rays to pass. 



The second view — a square —obtained through the green filter 

 only allows green rays to pass. 



The third view obtained with. a blue filter shows the blue circle, 

 the filter allowing only the blue rays to pass. When the three images 

 are superposed, a complete image of the objects in natural colours is 

 ()l)tained. 



In practice, liowever, in order to obtain all tints and tones— and 

 to obtain a pure white — it is indispensable to use filters which allow 

 rays from adjoining parts of the spectrum to pass. Thus, for a red 

 screen, a red-orange filter is used, for green, a green-blue, and for 

 blue, a blue-violet screen is used. 



Fig. 2 shows a projection of the designs or figures obtained with 

 the above-named screens ; on the left the negative and on the right 

 the positive. Notice that each view shows grey, which proves clearly 

 that the filter has allowed rays other than the primary coloui'S — ^red, 

 green and blue -to pass. 



Device to Save Exjjense. 



In an ordinary Cinematograph film, each view is l-S mm. high, 

 and is moved at a minimum velocity of 25 centimetres per second 

 with fourteen stops ; even with this speed one requires a well-construc- 

 ted machine in order to have a steady projection and no injury to the 

 films. 



The trichromic projection already described, however, requires a 

 speed of projection three times as great, i.e., 75 centimetres per second, 

 which would be very difficult with fourteen stops. 



Mons. Gaumont has got over the difficulty by diminishing by 

 one quarter the height of each image, so that three views take the 



