Proceedings of 1st International Symposium for Color Science and Art 2019

Appearance Reproduction of Photographic Prints
by Display Monitor
Yoshihiko Azuma, Tohru Tamura, Masao Inui, and Keiji Uchikawa*Tokyo Polytechnic Univ., 1583 Iiyama, Atsugi, Kanagawa 243-0297, Japan* Kanagawa Institute of Technology, 1030 Shimo-ogino, Atsugi, Kanagawa 243-0292, Japan
can realize (1) noted above. This system consists of thefollowing devices.
a. Hyperspectral camera
This device acquires photographic prints as
high-resolution digital images and color information ofeach pixel as spectral data.
b. Color signal processing engine
This engine calculates the spectral reflectance of eachpixel from the two-dimensional spectral data obtained by
the hyperspectral camera. From the spectral reflectance,
the engine also calculates XYZ tristimulus values of colors
under a given illumination light and converts the values
into RGB values for displaying colors on the display.
c. High-resolution display system
This display system reproduce the appearance ofphotographic print as the image on a display monitor
under an optimized observation environment.
Figure 1 shows the hyperspectral camera used in thestudy, HSC1804-CL2 (Hokkaido Satellite), which canacquire spectral images of all 141 bands at wavelengthintervals of 5 nm from wavelengths of 350 nm to 1050 nm.
When photographed from a distance of 50 cm, a subject of
330 mm (H) × 700 mm (V) is obtained as a digital image of1920 pixels (H) × 4000 pixels (V).

ABSTRACT
We examined a method for reproducing appearanceof photographic prints under recommended viewing
conditions by display monitors. We obtained an optimum
conversion of color information based on measurement
results of color patches on a photographic print and color
patches displayed on a monitor. Then we reproduced thecolors of the patches on the print as the patches on thedisplay using the conversion. As a result, the appearanceof the reproduced colors on the display was almost thesame as on the print when both the background andsurround were the same as the print.
1. INTRODUCTION
The SHADAI Gallery of Tokyo Polytechnic University
has a collection that includes over 10,000 valuable
photographic prints created by domestic and foreign
famous photographers, and some of these works are open
to the public at exhibitions that are held several times ayear. However, the number of works displayed is limited
due to given exhibition space. Therefore, digitalexhibitions are expected as a new means of showing.
In this study, we examined a method for reproducing
the appearance of photographic prints under a given
viewing condition on a display screen.
2. DIGITAL EXHIBITION SYSTEM
2.1 System concept
In the present photo exhibition gallery, the work is hungon the wall, illumination light is applied there, and theviewer can freely appreciate the details of the work fromthe position he or she wishes to see. In the digital
exhibition system as well, it is ideal to be able toappreciate the work reproduced on the screen of thedisplay, in a manner that appreciates the work in thegallery. Such a digital exhibition system needs to have thefollowing requirements.
(1) It should reproduce the color appearance of aphotographic print that changes according to the light
quality and color of the illumination light and theillumination angle.
(2) It should reproduce different texture according to thetype of photographic print material and reproducingtechnique.
(3) It should reproduce the change of the appearance ofthe work that changes according to the observation
position and angle of the viewer.
2.2 System configuration
In this study, as a first step, we develop a system thatFig. 1 Shooting with hyperspectral camera
3. REPRODUCTION OF COLOR APPEARANCE
3.1 Target color
Because photographic prints are sensitive to light, theintensity of exhibition lighting needs to be limited to someextent. Therefore, generally 50 lx or less is recommended
as the illuminance at the exhibition [1]. In this study, weaimed to reproduce the color appearance of photographic

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Proceedings of 1st International Symposium for Color Science and Art 2019
4. RESULTS & DISCUSSIONS
L * a * b * values were calculated from the XYZ valuesof the color patches for both of print and display, with thepaper white of the photographic print and the white of thedisplay being the respective reference white. The resultsof comparing the values of both on the a * b * plane areshown in Figure 3. Except for a few color charts, most ofthe color charts had the same value.

prints with illuminance satisfying this condition. We used atest chart No. 5-1 of the Imaging Society of Japan, madewith photographic paper, as a target sample (Figure 2).

Fig. 2 Test chart No. 5-1 of the Imaging Society ofJapan (color patches surrounded by red frames
were measured)This chart was stuck on a gray board paper which wasregarded as an exhibition wall, placed vertically on a desk,
and illuminated with a halogen light source (colortemperature 3300 K, illuminance 50 lx). Then, among thecolor patch series (B, G, R, Y, M, C, K) on the right side of
the chart, the 22 colors of the color patches in the thinnest
color, dark color, intermediate color, and paper white weremeasured with spectrophotometer SR3 (TOPCON). ThenXYZ tristimulus values of the 22 colors were obtained andthese values were taken as the target colors.
3.2 Reproduction of target color by display
In this study, liquid crystal display EIZO - CG248 - 4K
(23.8 inch, wide color gamut, number of display pixels
3840 × 2160) was used as display monitor. This display
was adopted from the viewpoint of resolution and stabilityof color reproduction [2]. In order to make the white
luminance and color of the display as close as possible tothe paper white of the illuminated photographic print, thedisplay was calibrated. Calibration was carried out with
ColorNavigator 6 so that the reference white of the display
had a color temperature of 4000 K, a luminance of 30 cd /m 2, and a gamma value of 1.0.
Under these conditions, XYZ tristimulus values of RGB
three primary colors and white and black were measured,and then a following conversion matrix from given XYZ
tristimulus values to RGB data for display was obtained
based on additive color mixing principle.

𝑅𝑅
0.511 −0.139
𝐺𝐺 ＝255･ −0.514
1.147
𝐵𝐵
0.003 −0.008−0.0890.030
0.059

Fig. 3 Comparison of color patches reproduced on
display and color patches of photographic print
In the result of displaying the RGB digital image readusing the scanner ES-10000G (EPSON), the color
difference in the L * a * b * space was 21.3 in the averagecolor difference and 52.3 in the maximum color difference.
In contrast, in the result after color correction, theaverage color difference was 3.5 and the maximum color
difference was 26.4. The large color difference was Y, M,and R dark color in order. In addition, when comparing thecolors of the displayed patches and the print patches
visually, it was confirmed that they are almost the samecolor.
In the high-density Y and R color patches in which thecolor difference of the reproduced color patches was large,
inverse conversion of the conversion of Expression (1)was performed, and a large color difference was observed
without returning to the original state. For these colors, it isthought that the conversion error due to the Expression (1)derived based on the color reproduction model appeared
largely.
5. SUMMARYWith the color correction by a 3 × 3, matrix conversion,
the color appearance of the photographic print patches
could be reproduced on the display with good accuracy. If
the hyperspectral camera is used, colors viewed underarbitrary illumination light can be reproduced.

𝑋𝑋𝑌𝑌 ・・・（1）𝑍𝑍

6. REFERENCES[1] T. Fujiwara, “Handbook of exhibition illumination forcurator”, pp. 12-13, Kodansha (2014).
[2] Y. Azuma, T. Tamura, M. Inui, and K. Uchikawa, “Abasic research on realistic texture reproduction ofphotographic print by display monitor”, Proc. ofACA2018, pp.603-607 (2018).

Using this equation, RGB values for display werecalculated from XYZ values of 22 color patches including
white of the target color, displayed as color patches on thedisplay screen, and XYZ tristimulus values of the patches
were measured with SR 3.

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