Images Perceived After Chromatic or Achromatic Contrast Sensitivity Losses

Abstract

Purpose. We simulate how subjects with losses in chromatic and achromatic contrast sensitivity perceive colored images by using the spatiochromatic corresponding pair algorithm. Methods. This is a generalized version of the algorithm by Capilla et al. (J Opt Soc Am (A) 2004;21:176 -186) for simulating color perception of color deviant subjects, which incorporates a simple spatial vision model, consisting of a linear filtering stage, with a band-pass achromatic filter and two low-pass chromatic ones, for the red-green and blue-yellow mechanisms. These filters, except for the global scaling, are the subject's contrast sensitivity functions measured along the cardinal directions of the color space. In its present form, the algorithm would serve to simulate alterations both in the spectral sensitivities and in the contrast sensitivities of the visual mechanisms. Results. After a preliminary theoretical study on the effect of frequency selective and overall reductions in the contrast sensitivity function of a single mechanism, we present cases of real subjects with glaucoma and diabetes, suffering alterations of different magnitude in the three mechanisms. Conclusions. The simulations allow us to learn about the different types of distortions that can be experienced by a subject with impaired contrast sensitivities (blur, haloes, color shifts, local or global contrast, brightness and colorfulness reductions, etc.) and highlight the difficulties arising when trying to predict the quality of the final image from the losses in the individual mechanisms.

Software for simulating dichromatic perception of video streams

“…The quality of the predictions depends on how well the models used describe the visual system. Although in subsequent versions models incorporating both chromatic and spatial properties of the visual system have been proposed, [12][13][14][15] the algorithm was applied in the first place to simulate images perceived by dichromatic subjects by implementing Eq. (1) with color vision models working separately on each image pixel.…”

“…Our research team has developed in the last few years an algorithm [12][13][14][15] that describes to normal subjects how subjects with variant vision perceive stationary images, in such a way that the user may (1) employ and compare different color vision models to explain a given anomaly, including the influence of observation conditions *Correspondence to: Dolores de Fez (e-mail: dolores.fez@ua.es).…”

“…Our research team has developed in the last few years an algorithm that describes to normal subjects how subjects with variant vision perceive stationary images, in such a way that the user may (1) employ and compare different color vision models to explain a given anomaly, including the influence of observation conditions and (2) configure certain visualization device‐dependent parameters. The different versions of this algorithm, which we explain in more detail below, have been implemented using a Matlab‐based library, Colorlab, developed in the Optics Department of the University of Valencia.…”

“…Basically, for a given image T (test), the corresponding pair algorithm computes the image S (simulation), verifying that a subject with variant color vision (problem or variant subject) perceives T in the same way as S would be perceived by a normal (or reference) subject. If we have models to predict the perception of normal and problem subjects (denoted by m n and m p , respectively), the image S may be found by solving the following equation: …”

The influence of the chromatic contrast change of digital prints on the measured contrast sensitivity function

“…M.J. Luque at al. [10] stated in their study that the achromatic filter is peaking around 3 to 4 cycles per degree (cpd), with a cutoff frequency at around 40 cpd, whereas the chromatic red-green and blue-yellow filters have cutoff frequencies at around 12 and 10 cpd, respectively. There have been several studies on measuring chromatic CSFs [2,9,11,12].…”