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Volume: 29 | Article ID: art00024
Can 'crispening' be explained by contrast gain?
  DOI :  10.2352/ISSN.2470-1173.2017.14.HVEI-141  Published OnlineJanuary 2017

'Crispening' is an effect whereby subjects perception of luminance is biased away from the background luminance level. The effect is strong, but may be reduced or abolished by the addition of a hue shift or an annulus that separates the tests stimuli from the background [16, 18]. In this paper we investigate whether the 'crispening' effect may arise from a simple gain mechanism that decreases sensitivity at luminance levels away from the background luminance level. The model takes as input the threshold versus intensity function, then decreases sensitivity via a gain mechanism. The supra-threshold percept is then estimated via Fechnerian integration of the resulting thresholds. We find that the model can predict subjects' luminance nonlinearities in all conditions as long as a parameter that controls the degree of gain is allowed to vary. Perhaps more interestingly, we find that the model can explain the luminance nonlinearity in the case where an annulus is present by treating the annulus as an additional background luminance level that also mediates gain. When multiple background luminance levels are included, the gain no longer produces the distinctive 'crispening' effect, although the gain still substantially affects the shape of the luminance nonlinearity. This may account for why 'crispening' is not observed when complex, real world scenes are investigated [2].

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David Kane, "Can 'crispening' be explained by contrast gain?in Proc. IS&T Int’l. Symp. on Electronic Imaging: Human Vision and Electronic Imaging,  2017,  pp 182 - 187,

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