(under subclass 432) Subject matter wherein light is passed through a specimen to be tested and compared in intensity with some other light, whose intensity is known or may be determined.
(1) Note. The light may be in beam form and the standard
light may also be passed through a light-modifying medium. The specimen and standard light may emanate from a common source.
SEE OR SEARCH THIS CLASS, SUBCLASS:
46+, for optical pyrometers with incandescent standards.
229+, for visual comparison photometers.
402+, for shade or color comparison.
443+, for film density determination involving comparison.
