December 2008
Volume 8, Issue 17
Free
OSA Fall Vision Meeting Abstract  |   December 2008
Visual sensitivity to isoluminant chromatic gradients with different spatial profiles
Author Affiliations
  • Luis Garcia-Suarez
    Bradford Optometry Colour and Lighting Lab, School of Life Sciences, University of Bradford, Bradford, UK
  • Alexa I. Ruppertsberg
    Bradford Optometry Colour and Lighting Lab, School of Life Sciences, University of Bradford, Bradford, UK
  • Marina Bloj
    Bradford Optometry Colour and Lighting Lab, School of Life Sciences, University of Bradford, Bradford, UK
Journal of Vision December 2008, Vol.8, 54. doi:10.1167/8.17.54
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      Luis Garcia-Suarez, Alexa I. Ruppertsberg, Marina Bloj; Visual sensitivity to isoluminant chromatic gradients with different spatial profiles. Journal of Vision 2008;8(17):54. doi: 10.1167/8.17.54.

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

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Abstract

Detection and discrimination thresholds were determined for isoluminant chromatic spatial gradients for four observers. The gradients (size 4*) were displayed against isoluminant non-uniform backgrounds. We have shown previously (Garcia-Suarez, Ruppertsberg & Bloj, 2008) that non-uniform backgrounds effectively disrupt the use of edges at the gradient boundary. The spatial chromatic profiles of the gradients were either linear or sinusoidal. Individual isoluminance settings were determined for each observer. Red-green and yellow-blue gradients were modulated around the neutral point along observers‘ respective physiological axes, L-M and S-(L+M).

For all observers, we found that sinusoidal red-green and yellow-blue gradients yielded detection thresholds 1.34 times lower than for linear gradients.

In the discrimination experiment, the test gradient was either stronger or weaker than a reference gradient. The latter was set to 8 times the contrast detection threshold of each observer. Thresholds for stronger and weaker conditions were the same. Although sensitivity to red-green gradients was 4 to 10 times higher than to blue-yellow gradients, the just noticeable difference between perceptually equated reference gradients and a stronger (or weaker) gradient was the same across spatial profiles and the two cardinal colour axes studied.

These results using chromatic stimuli are in agreement with our previous findings for achromatic gradients (Garcia-Suarez et al., 2008): the detection threshold differences between sinusoidal and linear gradients suggest that the visual system makes use of the difference between the gradient profiles.

Garcia-SuarezL.RuppertsbergA. I.BlojM. (2008). Visual sensitivity to achromatic gradients with different luminance profiles. Journal of Vision, 8 (6), 942a.

Garcia-Suarez, L. Ruppertsberg, A. I. Bloj, M. (2008). Visual sensitivity to isoluminant chromatic gradients with different spatial profiles [Abstract]. Journal of Vision, 8(17):54, 54a, http://journalofvision.org/8/17/54/, doi:10.1167/8.17.54. [CrossRef]
Footnotes
 LGS attendance at OSA Fall Meeting 2008 was made possible by a travel award from the College of Optometrist (UK) and from a Brain Travel Grant. LGS is sponsored by a PhD-studentship from the University of Bradford.
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