Preliminary note on the spectral energy
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Loyd A. Jones; A.L. Schoen
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Article
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1923
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Elsevier Science
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English
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comparison beam is controlled primarily by an adjustable sector shutter placed in a collimated beam of light between two elements of one of the lens combinations used to form an image oi the light source on the comparison target. 71'he photometric field is obtained by the use of the well-known Lumm