Ragona-Sciná's (1847) method for, and observations of, simultaneous color contrast

Robert P. O'Shea (Lead / Corresponding author), Stefano Brini, Nicholas J. Wade

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)
132 Downloads (Pure)


In 1847, Domenico Ragona-Sciná (1820-1892) published a method of optically superimposing images using an angled piece of colored glass. He showed that if one looks at a black, filled circle through the colored glass and superimposes on it the reflection from the glass of something white, the filled circle looks tinted with the complementary color of the background: simultaneous color contrast or contrast color. Although Ragona-Sciná's method and his observation have been cited into the 21st century, the former for its simplicity and the latter for its challenges to early theories of color vision, some errors have crept in and the phenomenon still lacks an agreed-on explanation. We provide some biographical information about Ragona-Sciná, set the method and the observation into their historical and theoretical contexts, and give a translation into English of Ragona-Sciná's Italian-language paper.

Original languageEnglish
Number of pages13
Issue number2
Publication statusPublished - 28 Apr 2016


  • Color perception
  • History
  • Methods for research in visual perception
  • Multi-field tachistoscope
  • Optical superimposition
  • Ragona
  • Simultaneous color contrast


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