CH. XI] 



MOVING PICTURE APPARATUS 



405 



directly in front of the condenser. This is not a good plan as it 

 cuts down the light from the condenser, and as the opening is not 

 round but a quadrangle it often leads to queer shadows on the 

 screen. Some makers provide a stationary slide-carrier opposite 

 the magic lantern objective so that the whole face of the condenser 

 is free when it is opposite the moving picture objective ; this is a 

 better method than the above. 



FIG. 224. DOUBLE DISSOLVING MODEL C BALOPTICON WITH EDISON 

 MOVING PICTURE ATTACHMENT. 



(Cut loaned by the Bausch & Lomb Optical Co.). 



569. The moving picture head. This contains all of the ele- 

 ments of the moving picture machine except the arrangement for 

 lighting. The moving picture head holds the objective and con- 

 tains the film-moving mechanism and the aperture plate. 



570. Aperture plate. Considered optically the aperture plate 

 which serves as a frame for the picture on the film is the most 

 important part of the moving picture head. 



