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Bong-Soo KIM In-Ho SONG Eun-Su KIM Sung-Hak LEE Soo-Wook JANG Kyu-Ik SOHNG
In this paper, a chromatic adaptation model (CAM) based on the dependence on LMS cone responses of the human visual system (HVS) is proposed for TV and PC monitors under a variety of viewing conditions. We derived the proposed CAM based on Breneman's corresponding color data. The results of the experiments were carried out to assess the proposed model performance in terms of color fidelity by comparing complex images on a LCD monitor. We confirmed that the proposed model performed better to predict corresponding colors under various viewing conditions. Therefore, the reproduced colors, which are viewed in real surround viewing conditions, are perceived the same as original object colors, when the proposed CAM was applied to color display devices such as CRT, LCD, and PDP.
Sung-Hak LEE Soo-Wook JANG Eun-Su KIM Kyu-Ik SOHNG
We investigated physical conditions for optimum display systems on various TV viewing conditions, and found that visual brightness function could be derived from relationships between Steven's power law and Bartleson-Breneman's brightness function, and that the optimum physical contrast ratio and compensated gamma for display system with adaptation luminance level could be obtained from the proposed brightness function.
Eun-Su KIM Soo-Wook JANG Yong-Dae KWON Chan-Ho HAN Kyu-Ik SOHNG
In this paper, a simple and practical corresponding-color reproduction model based on the chromatic adaptation of the human visual system (HVS), named a modified von Kries chromatic-adaptation model, is proposed for TV and PC monitors under a variety of viewing conditions. We derived the proposed corresponding-color reproduction model based on Breneman's corresponding-color data. The proposed model has a 1-2% less error than Fairchild's and Breneman's model, 11.5% less error than von Kries' model and 60% less error than CIECAM97s' model in terms of color reproduction errors, (). Also, these tendency is similar in color reproduction errors, . We implemented a corresponding-color reproduction system using the proposed model under a variety of viewing conditions. For the determination of viewing conditions, illuminant correlated color temperatures (CCTs) are measured by yellow/cyan sensors. These measured surround illuminant CCTs can estimate an adaptated neutral point of the HVS in TV viewing conditions. Experiments were carried out to assess the proposed model performance in terms of color fidelity by comparing complex images on a LCD monitor under illuminants from 2500 K to 7500 K. We confirmed that the implemented system using the proposed model can predict corresponding-color data very well under a variety of viewing conditions. Therefore, by applying the proposed model and system to the LCD, the reproduction colors viewed in real surrounding viewing conditions on the LCD could appear the same as the original object colors under standard viewing conditions. Furthermore, they could be applied to any other color display device such as a CRT, a PDP, and a DLP in order to get better reproduction colors.
In-Ho SONG Bong-Soo KIM Eun-Su KIM Sung-Hak LEE Soo-Wook JANG Kyu-Ik SOHNG
Color reproductions in most LCD are quite different from those of standard CRT (cathode ray tube) monitor display because of the nonlinear characteristic in subtractive color reproduction. Moreover, gray scale CCT (correlated color temperature) reproductions in a typical mobile phone LCD depend on the input RGB levels. A simple LUT (Look-up table) method for constant gray scale CCT and gamma characteristic of mobile phone LCD is presented in this paper. We investigate the mobile phone LCD's characteristic of compensation of CCT with using the LUT. LCD's CCT is maintaining about 7500 K, which is the target CCT of mobile phone LCD in this paper. Also LCD's gamma is similar to target gamma.
Sung-Hak LEE Soo-Wook JANG Eun-Su KIM Sang-Hoon LEE Kyu-Ik SOHNG
The pulsed backlight system has been introduced for reducing motion blurs of LCDs in high motion pictures. But applying the pulsed backlight, full screen flicker and inconsistency of transmissivity for entire frame at a lightening time should be considered. This paper discusses the analysis of blurs in high motion pictures and proposes the design method for more suitable display terminal of LCDs.
Eun-Su KIM Soo-Wook JANG Sung-Hak LEE Tae-Young JUNG Kyu-Ik SOHNG
The gamma correction for the CMOS image sensors are implemented by the method of piecewise linear approximation through a look-up table. In this paper, we propose a quantitative criterion to select the piece linear segment with the same output interval for the reduction of the error between the value of piece linear approximation and gamma correction. After the gamma correction is implemented, the average error occurred by implementing color interpolation in each segment is a basis for the optimum selecting of the piece linear segment of the gamma correction for the CMOS image sensors.
Eun-Su KIM Sung-Hak LEE Soo-Wook JANG Kyu-Ik SOHNG
The RGB signals generated by different cameras are not equal for the same scene. Therefore, cameras are characterized based on a CIE standard colorimetric observer. One method of deriving a colorimetric characterization matrix between camera RGB output signals and CIE XYZ tristimulus values is least squares polynomial modeling. Yet, this involves tedious experiments to obtain a camera transfer matrix under various white balance points for the same camera. Accordingly, the current paper proposes a new method for obtaining camera transfer matrices under different white balances using a 33 camera transfer matrix under a specific white balance point.