Color changes in the red-green plates of the 50-year-old AO HRR color vision test

The original AO HRR color vision test has been considered by many as one of the best plate tests. It is still accepted by many governmental agencies for color vision certification. In their 1954 publication, Hardy, Rand, and Rittler stated that specially compounded inks were used for printing to avoid color changes with time. Fifty years later, it is both important and interesting to determine whether the wear and tear cause significant color changes. The chance finding of a never-used second edition offers an opportunity to evaluate the color changes. A GretagMacbeth Spectrolino spectrophotometer was used to measure the chromaticities of the never-used book, and an extensively used book. Four plates (#4, 7, 13, 16), selected randomly from the four red-green sections, were analyzed. The colored dots from each of the eight plates were plotted on a CIE chromaticity diagram. Isocolor lines were drawn to evaluate chromatic alignment. Chromaticities for plates #4 and 7 are significantly different between the two books. With regard to alignment with isocolor lines, the extensively used book is better than the never-used book for plate #4. There is significant misalignment on plate #7 for both books. Chromaticities for plates #13 and 16 are essentially identical between books, all with good alignment with isocolor lines. The overall comparison shows that the chromatic alignment characteristics of the extensively used book are not worse than the never-used book. Since colors in these plates have to be aligned with both the protan and deutan axes, any significant color changes would have disturbed this delicate requirement. The findings of many plates with good alignment, and the lack of differences on plates #13 and 16 between books, suggest that there are no significant color changes over time. Differences between books on plates #4 and 7 were likely the result of the original printing process.