(under subclass 213) Subject matter including an aperture in the optical path whose aperture size may be controlled to vary the illumination passing therethrough from a location whose light intensity is to be determined or including a plurality of apertures of different sizes one of which may be selected to pass a predetermined quantity of light, the purpose in both cases being to reduce the visible illumination to render the viewed object or indicia markings barely visible.
(1) Note. The subject matter classified here may include scales for indicating the illumination intensity for general illumination purposes or for photos:graphic purposes. The photometers classified here are of the visual type in the sense that the eye itself is the detector.
SEE OR SEARCH THIS CLASS, SUBCLASS:
43+, for optical pyrometers of the visual type.
SEE OR SEARCH CLASS
235, Registers,
64.7, for photos:graphic calculators. 352, Optics: Motion Pictures,
139, for visual photometers combined with motion picture cameras.
396, Photography,
213+, for visual photometers combined with cameras.
