We developed the method to adjust a display to a predetermined state and to make ICC display profiles with human eyes. In our method, in order to measure the tone reproduction curve of a display device, the brightness and hue of a continuous tone image is adjusted to the brightness and hue of a binary image. In addition, three pairs of images having different values of brightness are used. These methods enable one to measure the complex tone reproduction curve. Furthermore, the color of the display white is adjusted to the color of a white object under the viewing illuminant. Our method can adjust the display white for any viewing illuminant. To bear out the color matching accuracy of our method, two kinds of experiments were carried out for three LCDs, and three subjects. First, we measured the chroma of gray. The result was that the chroma of the display adjusted by our method was smaller than the chroma of the unadjusted display. Second, we simulated the color of DDCP on the display and measured the matching accuracy displaying the ISO 12642 color chart. Though the average E ∆ was 13.25 to 14.68 with the un-adjusted display, 2.87 to 6.85 for the adjusted display by our method. Thus, our method could reduce the color difference between both devices. These results show the display adjusted by our method has enough accuracy to use for soft proofing.

We have developed a method to calibrate a display to a predetermined state and to make an ICC display profile by visual calibration for soft proofing. Our method adjusts a color of display white point to a color of a white object under a viewing illuminant, so our method can calibrate the display white point for any viewing illuminant. In order to calibrate the tone reproduction curve of a display, the brightness and hue of a continuous tone image is adjusted to the brightness and hue of a binary image. In addition, three pairs of images having different values of brightness are used. These methods can calibrate the display which has complex tone reproduction curve like LCD displays. In Electronic Imaging 2005, we reported that these methods can calibrate tone reproduction curves of LCD displays accurately 1 .In this paper, we evaluated the matching accuracy between display white point and paper white under various illuminances and color temperatures to bear out the effect of our method under practical illumination. We found from this experiment that the matching accuracy was almost the same in all illumination conditions. Furthermore, all subjects calibrated the chromaticity of display white point more bluish than the chromaticity of paper white in all illumination conditions, and the dispersion of yellow-blue direction was larger than that of red-green direction. This yellow-blue direction was almost the same as the long axis of MacAdam ellipse.We also evaluated the capability of color discrimination between display and paper in various illumination conditions. At 500lx or less, many subjects made judgments that the color of display white point was similar as the color of paper white when color difference between display and paper was small, but the correlation of color difference with judgement was small at 1000lx or more. The cause of these results is the maximum luminance of the display was darker than that of paper at 1000lx or more. These results suggest that ISO 3664:2000 P2 condition is appropriate to compare the image on computer display with that on paper at the same time.

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Abstract— Soft proofing, which can confirm the color reproduction of printed matter on a monitor, is coming into wide use in the field of graphic arts. However, there is a problem in that the color on the monitor looks different from that of printed matter, even though the L*a*b* value of the monitor's white point has been adjusted to that of the paper by using a spectroradiometer. After the color rendition of an LCD is visually adjusted to that of the paper, the measured color of the LCD shows color with L*a*b* values corresponding to a more greenish‐blue white than that of paper. For CRTs, this corresponds to a more bluish‐white. In this paper, it was assumed that bright lines in the measured spectrums of the monitors and the illuminations spread to the next wavelength band by the optical systems of the spectroradiometer. To solve the problem, a method is proposed to enhance the bright line by using a three‐tap digital filter. The effect of this method on two types of monitors under three types of illumination is also reported. After enhancing the bright lines, ΔE between the monitor and paper becomes smaller than that for the original one.