Estimation of the Helmholtz–Kohlrausch effect for natural images

Abstract

-The Helmholtz-Kohlrausch (H-K) effect is the phenomenon in which two color stimuli have the same luminance but different chroma in a certain hue, so the perceived brightness induced by the two stimuli are different. In expanding gamut, it is necessary to consider the H-K effect. A quantification of the H-K effect is required in order to evaluate and develop display devices for which the change of perceived brightness of gamut expansion must be considered. For quantification of the H-K effect, prediction equations that can derive the equivalent luminance in a single color image have been proposed in previous studies. However, these equations have not been applied to natural images that are important. Therefore, the purpose of this study is to quantify the H-K effect by deriving calculated values for natural images. For this purpose, first, we conducted the quantification of the H-K effect in natural images by deriving the equivalent luminance as calculated values expanding the three prediction equations proposed in previous studies. Next, we carried out a subjective evaluation experiment by varying image's chroma and luminance. We then verified the effectiveness of the calculated values by comparing them with the result from the experiment.

Image quality equivalence between peak luminance and chromaticity gamut

“…It is apparent at a glance that the slopes of these lines, which show the change in lightness ( J IPT ) relative to the the change in chroma ( C IPT ), differ from one image to another. This is consistent with the claims suggested by the previous studies that the impact of the Hunt effect or the H‐K effect could vary from one image to another [15,16] and the effect of varying color gamut area and luminance level on image quality is dependant on image content [9] . The average slope magnitude over the entire measurements was ‐0.125, which means that, on average, image quality is maintained when 0.125% of lightness level decreases with the increase of 1.0% in chroma level.…”

“…These color appearance phenomena complicate the trade‐off relationship. Moreover, previous studies [15,16] have pointed out that the effect of these color appearance phenomena varies with not only changes in the physical parameters but also change in image content. For example, the H‐K effect appears in highly chromatic images as expanding the area of the color gamut of a display device; however, the H‐K effect is less prominent in lower‐chroma images with the same physical change.…”

An Advanced Pre-Processing Pipeline to Improve Automated Photogrammetric Reconstructions of Architectural Scenes

“…They assign different grayscale values to isoluminant colors, altering the luminance information and using the chrominance information. In order to increase or decrease the "correct" luminance to differentiate isoluminant colors, these methods exploit a result from studies on human color perception, known as the Helmholtz-Kohlrausch (H-K) effect [52]. The H-K effect states that the perceived lightness of a stimulus changes as a function of the chroma.…”

Color‐by‐Blue QD‐Emissive LCD Enabled by Replacing RGB Color Filters with Narrow‐Band GR InP/ZnSeS/ZnS QD Films

“…This is known as the Helmholtz–Kohlrausch (H–K) effect. The more saturated color of the display can be perceived by the eye as brighter . As shown in Figure , the perceived quality metric is defined quantitatively as the display quality, which is affected by both the luminance and color gamut.…”