Projection Apparatus (1917)

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Bausch & Lomb Optical Company Attachments While the Model C Balopticon is primarily a lantern for slide projection, it can nevertheless be fitted with attachments for the projection of opaque objects, microscopical specimens or large transparent objects held in a horizontal plane. Attachment for Opaque Objects Figure 5—Model C Attachment for Opaque Objects. The attachment for the projection of opaque objects, such as photographs, illustrations from text books, post cards, etc., Figure 5, can be very easily attached to the lamp house portion of the Model C Balopticon by means of the sliding ways on the front of the slide carrier support which regularly carries the rear end of the bellows. The front standard and rods are easily removed. If the apparatus is to be used at a comparatively short distance from the screen, the 12- inch focus lens of 2%6-inch diameter can be satisfactorily used, but for distances of 20 feet or more from the screen we recommend the use of the 4-inch diameter, 15 or 18-inch focus lens, since the illumination is increased according to the square of the diameter of the lens. The use of the attachment is recommended only when the apparatus can be placed at a comparatively short distance from the screen (25 feet) in a well darkened room and with an arc lamp operating on at least 25 amperes of current. 32