CA. 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.
F Hi. 224. Double Dissolving Model C Balopticon with Edison-
Moving Picture Attachment.
(Cut loaned by the Bausch or 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.