November 2004
Volume 4, Issue 11
OSA Fall Vision Meeting Abstract  |   November 2004
Three ways to find a tritan line
Author Affiliations
  • Hannah Smithson
    Institute of Ophthalmology, University of College London, UNITED KINGDOM
  • Angela Bourke
    Institute of Ophthalmology, University of College London, UNITED KINGDOM
  • Qasim Zaidi
    SUNY College of Optometry, USA
  • John Mollon
    University of Cambridge, UNITED KINGDOM
  • Andrew Stockman
    Institute of Ophthalmology, University of College London, UNITED KINGDOM
Journal of Vision November 2004, Vol.4, 83. doi:
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      Hannah Smithson, Angela Bourke, Qasim Zaidi, John Mollon, Andrew Stockman; Three ways to find a tritan line. Journal of Vision 2004;4(11):83.

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      © ARVO (1962-2015); The Authors (2016-present)

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We compare three methods of locating a tritan line. Method I exploits ‘transient tritanopia’ (Mollon & Polden, 1975). If the abrupt offset of a yellow field produces a selective loss of sensitivity in the S-opponent mechanism, the direction in colour space along which the loss of sensitivity is greatest should locate the tritan line. Method II uses a blue adapting field to elevate selectively S-cone detection thresholds (e.g. Webster, DeValois & Switkes, 1990). Method III is a performance version of the minimally distinct border method (Tansley & Boynton, 1976). Our stimulus comprises two coloured areas that are separated by a jagged (sawtooth) border. Observers are required to discriminate between sawteeth that are inverted or non-inverted in spatial sign. Since the task requires resolution of high spatial frequencies, performance should be poorest when the border is defined only by the S-cone signal.

We test the extent to which Methods I and II are dependent on the spectral composition of the adapting field. Estimates from both methods may be biased by preferential adaptation of the L- or M-cones. Of the two methods, Method I seems less influenced by moderate changes in the L:M component of the adapting field. Importantly, all three methods, if properly applied, converge to a common estimate of the tritan line for a given observer and retinal eccentricity. We discuss the limitations and relative merits of each method.

Smithson, H., Bourke, A., Zaidi, Q., Mollon, J., Stockman, A.(2004). Three ways to find a tritan line [Abstract]. Journal of Vision, 4( 11): 83, 83a,, doi:10.1167/4.11.83. [CrossRef]
 Supported by the Wellcome Trust.

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