Image quality evaluation of HDR displays

Paper (473K) | Contents (901K)


Introduction

The demand of accurate and pleasant image reproduction for displays has been important in recent years. Being limited by their small dynamic range, however, the usual displays can hardly reproduce the actual luminance of real scenes effectively. In response to the requirement of displaying image contents with higher dynamic range and better luminance accuracy, the high dynamic range (HDR) displays have been developed. Differing from the traditional standard dynamic range (SDR) displays, the HDR displays generally have higher peak brightness and lower minimum luminance level, thus providing a wider dynamic range to reproduce more details of the presented images or videos. To reproduce HDR contents, both HDR signal source and HDR display device are necessary. The former provides the scene’s real luminance information when being captured, and the latter uses a device-independent electro-optical transfer function (EOTF), namely perceptual quantizer (PQ), to convert the electric source signal to the optical output signal, producing the same luminance as recorded in the HDR image contents. The previous studies have pointed out that the HDR image contents have obvious advantages over the SDR image contents. On the other hand, the large-size OLED HDR displays have been developed, which can present very low blackness and rather high perceptual contrast. Thereby it is desiderated to investigate and further compare the performances of HDR displays with different coloring technologies as well as the external and internal factors that affect the display quality.

In this project, a series of psychophysical experiments were carried out to evaluate the image quality of three HDR TVs with different luminous mechanisms and panel technologies, and further to discuss how the image attributes and viewing conditions impact the overall preference of the observers for the HDR displays.

Figures

Figure 1. The color gamuts of the three test displays as well as sRGB and DCI-P3 for comparisons at CIE1976 u'v' diagram.

Figure 2.Setup for subjective experiment (top view).

Figure 3. Overview of the involved test images. The rows of images correspond to the attribute of (a) Peak brightness, (b) Blackness, (c) Colorfulness, (d) Gradation, in which the former 3 are for High gradation and the others are for Low gradation, (e) Contrast, (f) Reality, and (g) Artifacts.

Figure 4. The overall results of the static image test (scale value method). The figures represent viewing conditions of (a) dark, front view, (b) dark, side view, (c) 200 lx ambient lighting, front view, and (d) 200 lx ambient lighting, side view.

Figure 5. The CV (coefficient of variation) values of image attributes and overall preference between individual and average in the condition of dark and front view.

Figure 6. The grand total scale value scores of the static image test for 3 displays: (a) the average image attributes scores, and (b) the overall preference scores.

Figure 7. scale value results of image attributes and overall preference for individual test images in the condition of dark and front view.

Publication

Reference

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