Letter | Published:

[Letters to Editor]

Nature volume 160, page 24 (05 July 1947) | Download Citation



Mr. R. G. Horner and Mr. E. T. Purslow have made a detailed study of the fact that the red-green ratio required to match a given yellow in the anomaloscope is dependent to a marked extent upon the distance of viewing (or the angular field). I observed this effect in my anomaloscope1, and one of my students made a study of it. He is now unfortunately inaccessible, being in the Navy, and I am unable to quote his measurements; but his findings were approximately those given by Horner and Purslow, namely, a rapid change in the ratio at small distances, settling down to a constant value where the distance is large, that is, the angular field sufficiently small.

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  1. 1.

    J. Sci. Instr. 22, 15 (1945).

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  1. Physiology Institute, University College, Cardiff. April 5.

    • J. H. SHAXBY


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