68o OPTIC PROJECTION 



If any individual should be mentioned in connection with the projection 

 microscope, it is Kepler, for in his Dioptrics, 161 1, he showed the advantage of 

 adding an amplifier in projection, and also a second convex lens (ocular), to 

 magnify the real image of the objective, and also at the same time to render it 

 erect. See Opera Omnia, vol. ii, pp. 549-550, 555. 



3. Moving Pictures 



Moving picture projection is like micro-projection when no ocular is used. 

 The screen distance is usually rather great and the many slightly differing 

 pictures are changed so rapidly that the successive screen images seem to fuse 

 together and thus give the appearance of motion. 



The first step in getting moving pictures was an investigation of persistence 

 of vision by momentary glimpses of similar moving objects. The men inves- 

 tigating the matter were all physicists, and the results of their observations 

 were given in scientific papers. See in the bibliography papers by Fara- 

 day, Plateau, Horner and Stampfer. The paper on the magic disc by Plateau 

 was dated Jan., 1833, and the paper of Horner on the da3daleum (zoetrope) 

 was dated 1834, as was also the paper of Stampfer on the magic disc. Both 

 the magic disc (fig. 408) and the zoetrope (fig. 409) give the appearance of 

 movement with great satisfaction. 



As the instruments were for one or at most for very few observers, the magic 

 lantern was called in to give screen images so that many could see at the same 

 time. The magic lantern was used successfully by Uchatius in 1853. He 

 used several (as many as 12) slightly differing transparencies, each transparency 

 having its own projection objective. The objectives were all directed toward 

 the same point on the screen, hence the images all appeared in the same place. 

 A lime light and condenser were attached to a crank, and moved from picture 

 to picture in rapid succession, and the projected images gave the appearance 

 of movement as perfectly as did the magic disc. 



It was also natural that the new art of photography should be called upon 

 to depict the various phases of a moving body for use in place of the drawings 

 which had been previously used; this was suggested by Plateau about 1848. 

 In 1870 Heyl realized this possibility by arranging a series of photographic 

 transparencies of posed motion, and projecting them on the screen. The 

 transparencies were arranged on the edge of a large disc, and by the step by 

 step movement of the disc the successive transparencies were brought in the 

 axis of the magic lantern. To prevent the blur while the pictures were changed , 

 a two wing shutter was used to cut off the view. This method of projecting 

 was very successful and required only one projection objective, consequently 

 the number of pictures was limited only by the practicable size of the rotating 

 disc. 



Up to 1872 the pictures used were either drawings or photographic trans- 

 parencies of posed movements, not photographs of movement in continuous 

 change as at present. 



