The non-linear nature of the human visual response to achromatic contrast is a key element to improve the performance in achromatic image coding. Expressing transform coefficients in the appropriate contrast units is relevant when some particular non-linear processing hasto be applied. In the achromatic case, the use of non-linear psychophysical models is straightforward since achromatic contra...

Text can be depicted by luminance contrast (i.e., differences in luminance between characters and background) or by color contrast (i.e., differences in chromaticity). We used a psychophysical method to measure the reading speeds of eight normal and ten low-vision subjects for text displayed on a color monitor. Reading speed was measured as a function of luminance contrast, color contrast (deri...

PURPOSE To determine whether face perception can be equalized across the visual field by scaling size and contrast simultaneously. METHODS Contrast sensitivities were measured for detection (N = 1) and identification (N = 2-8) of a target face as a function of size (0.4 degrees-10 degrees) across eccentricities (E = 0 degrees-10 degrees). RESULTS In all conditions contrast sensitivity first...

We used a hue-scaling task to examine changes in color perception resulting from adaptation or induction to color contrast in spatially-varying backgrounds. Observers judged the perceived color of tests after or while viewing backgrounds composed of color differences along selected axes in color space. Both contrast adaptation and contrast induction produced large and selective shifts in percei...

purpose: to evaluate visual function in patients with different types of light-filtering intraocular lenses (iols) methods: in this prospective comparative clinical study cataract patients with different types of iols in khatam-al-anbia eye hospital, mashhad were enrolled and followed for three months postoperatively. corrected distance visual acuity (cdva), color discrimination under photopic ...

We used psychophysical tests to evaluate spatial vision in 15 subjects with a clinical history of chronic alcoholism by measuring luminance contrast sensitivity and color discrimination. The subjects were initially subjected to clinical inquiry and ophthalmological exam. Subjects then performed psychophysical tests to measure spatial contrast thresholds using sine wave gratings of different spa...

In many applications there is a need to visualize multidimensional data sets. Using spatial relationships alone, display is limited to two or three dimensions. The use of color, in addition to spatial relationships, increases the dimensionality of the data that can be effectively visualized. Use of color is usually achieved through the application of color tables. The generation of color tables...