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 the centered circularity of chroma loci expected of a uniform chromaticity-scale system, and it was given due consideration in choosing the system for the final smoothing of the data. It was rejected, however, because the neutral point changes rapidly with the value level and there would be practical difficulties in combining the determinations made at the different levels. The adapted U.C.S. system was rejected because it did not eliminate distortion, especially near black and white. The points in favor of the I.C.I. system are its standard character and wide acceptance. There is also the essential fact that like the other three systems, it does not present sharp irregularities which would be confused with those to be smoothed out of the Munsell data.

The present committee on the spacing of the Munsell colors was appointed by L. A. Jones in 1937 as a Subcommittee of the Colorimetry Committee of the Optical Society of America. The present personnel includes B. R. Bellamy, H. P. Gage, D. B. Judd, Dorothy Nickerson, W. B. VanArsdel, and S. M. Newhall.

Ratio method

The ratio method, which has been relied upon from the beginning in this survey, consists in the estimation by direct impression of the ratio of