In recent years, new display technologies have emerged that are capable of producing colors that exceed the color gamut of broadcast standards. On the other hand, most video content currently remains compliant with the EBU standard and as such, there is a need for color mapping algorithms that make optimal use of the wider gamut of these new displays. To identify appropriate color mapping strategies, we have developed, implemented, and evaluated several approaches to gamut extension. The color rendering performance and robustness to different image content of these algorithms were evaluated against a reference (true-color) mapping. To this end, two psychophysical experiments were conducted using a simulated and actual wide-gamut display. Results show that the preferred algorithm had a dependency on image content, especially for images with skin tones. In both experiments, however, there was preference shown for the algorithm that balances chroma and lightness modulations as a function of the input lightness. The newly designed extension algorithms consistently outperformed true-color mapping, thus confirming the benefit of appropriate mapping on wide-gamut displays.
LCD televisions have LC response times and hold-type data cycles that contribute to the appearance of blur when objects are in motion on the screen. New algorithms based on studies of the human visual system's sensitivity to motion are being developed to compensate for these artifacts. This paper describes a series of experiments that incorporate eyetracking in the psychophysical determination of spatio-velocity contrast sensitivity in order to build on the 2D spatiovelocity contrast sensitivity function (CSF) model first described by Kelly and later refined by Daly. We explore whether the velocity of the eye has an additional effect on sensitivity and whether the model can be used to predict sensitivity to more complex stimuli. There were a total of five experiments performed in this research. The first four experiments utilized Gabor patterns with three different spatial and temporal frequencies and were used to investigate and/or populate the 2D spatio-velocity CSF. The fifth experiment utilized a disembodied edge and was used to validate the model. All experiments used a two interval forced choice (2IFC) method of constant stimuli guided by a QUEST routine to determine thresholds. The results showed that sensitivity to motion was determined by the retinal velocity produced by the Gabor patterns regardless of the type of motion of the eye. Based on the results of these experiments the parameters for the spatio-velocity CSF model were optimized to our experimental conditions.
Displays are coming on the market that can produce a larger range of colors over EBU and this has led to much research on the topic of how to use the additional color gamut volume provided by the displays. Some research has focused on different methods to map colors from small to large gamuts, whereas this paper focuses on defining the required gamut boundaries for natural content. Two gamuts were created from the results of a psychophysical experiment that asked observers to choose their preferred image in terms of saturation. One gamut corresponded to the median value of their choices and the second gamut corresponded to the 90% value of their choices. The results indicated that even at the 90% value, the resulting gamut was smaller than that of the wide-gamut display for most hues and actually closer to EBU for some hues. These results are display independent, at least when considering modern displays that can reach luminance values above 250cd/m 2 .
An approach is introduced for building accurate and compact color look-up tables (CLUTs) to describe the colorimetric performance of liquid crystal display (LCD) devices. In an experiment, a novel analysis technique was found to be useful in guiding the choice of samples used in the building of the CLUT. The experiment demonstrated that an 8x8x8 CLUT produced through the new sampling method delivered comparable results to an 18x18x18 made from a different sampling technique. The technique will allow for future automation of choosing optimal samples for building LCD CLUTs.
Abstract— Recent commercial liquid‐crystal‐display (LCD) televisions are larger and brighter than traditional televisions, thus impacting the viewing conditions in which they are viewed. These changes in viewing conditions may require different electro‐optical transfer functions (EOTFs) for LCD TVs than those for conventional TVs. Here, the way various EOTFs affect the preferred image quality of test images with changes in brightness and surround illumination conditions are examined. The first method used a gain, offset, and gamma (GOG) function with a range of gamma values, and the second method altered the intrinsic EOTFs. Image preference for the simulated EOTFs was determined using a paired‐comparison experiment for ten images. The first experiment took place in a darkened room at two display luminance levels. The results indicated that a gamma of 1.6 was most preferred overall although more so at a lower screen luminance level. In a second experiment, the procedure was repeated with a dim surround of 10% of the display's white point. With this surround, preference for a gamma value of around 1.6 at both screen luminance levels was more enhanced. These results indicated that image preference for different EOTFs is dependent on display luminance and that this dependence is maintained with a dim surround.
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