J. of IEIJ Vol.86, No.4

The Abstracts of the Papers
J.Illum. Engng. Inst. Jpn. Vol. 86, 2002

Experimental Study of the Effects of Artificial Lighting on the Maturing of Figs
Tetsuo KADONAGA, Shinichi KOHSAKA and Hitoshi YANAGIHARA

 The maturation of figs under varied fluorescent lighting conditions was studied. Two commercial fluorescent light sources were tested. The first was a tube type used for copy machines. The second was a three-band fluorescent lamp. The third lighting condition was created by combining both tube types. Testing was done using different daily lighting cycles. The input power during on-time was kept constant for all test conditions. Light and temperature are the main factors affecting the maturing of figs. The degree of maturation was identified by color changes and quantitative measurement by assessing such characteristics as weight, flesh hardness, and sugar content. The experimental results revealed that mixed light sources with 16 hours per day of irradiation were the most effective inpractical greenhouse cultivation.

KEYWORDS : artificial lighting, fig fruit, greenhouse cultivation, irradiation time, maturity

The Concept of Visual Acuity Ratio to the Maximum Level of Individual Visual Acuity
- The Evaluation Method of Background Luminance and Visual Distance on Visibility Taking into Account of Individual Visual Acuity -
Yuki AKIZUKI and Youko INOUE

 We use the maximum level of individual visual acuity (MVA) as an index for the individual visual ability. Also, we define the concept of the ratio of visual acuity under various environmental conditions for the MVA as Visual Acuity Ratio (VAR), in order to describe differences between individual visibility.
 An experiment was carried out using various levels of background luminance and visual distance. The visual acuity of subjects in two age groups (Young and Aged) was measured by using Landolt's eyechart (luminance contrast : 0.93).The Aged subjects' vision was corrected by two kinds of spectacles: ones for myopia/presbyopia.
  Under conditions providing sufficient visual acuity, the subjects' order of individual visual acuity was unchanged. Therefore, MVA can be used as an index for the visual ability of the individual. Regardless of corrected conditions, the individual visual acuity reaches the maximum level under 800cd/m² and the corrected position. The results of the eyesight test can be used as a substitution for MVA.
  Visual acuity is changing under environmental conditions, and a degree of the changes varies with age, corrected conditions, and differences in visual acuity. Under the corrected position, the relationship between background luminance and VAR is constant regardless of age group, corrected conditions and differences of visual acuity. The relationship between visual distance and VAR differs by age and corrected conditions. However, in the neighborhood of the corrected position, the relationship between visual distance and VAR is constant regardless of differences between individual visibility. The concept of VAR is applicable to past studies.

KEYWORDS : visual acuity, luminance, visual distance, Visual acuity Ratio, age, individual differences

Brightness in Natural Environments Evaluated Using the Brightness Size of Recognized Visual Space of Illumination
Hideki YAMAGUCHI, Hiroyuki SHINODA and Mitsuo IKEDA

 Understanding illumination is necessary for the perception of color and brightness in an object's surface. We call such understanding the recognized visual space of illumination, or RVSI. In particular, we use the term ‘brightness size’ of RVSI to describe an observer's perception about the intensity of illumination. The brightness size of RVSI is evaluated using the border luminance between surface color and unnatural surface color modes. We established a new estimation method of space brightness in natural environments and investigated what determines the brightness size of RVSI. We measured the border luminance of the test patch (N5 gray, mat) to test three candidates for determining the size: illuminance(1), spatially averaged luminance across a visual field(2), and highest luminance(3). The border luminance was proportional to the illuminance and was almost equal to the luminance of the object with the highest lightness. However, there was no effect from the luminance of the object with the light-source color mode, regardless of its luminance. The effect from the averaged luminance was not significant. We concluded the illuminance to be a major determinant of the brightness size of RVSI.

KEYWORDS : space brightness, recognized visual space of illumination (RVSI), brightness size of RVSI, color appearance mode, natural environment

Analysis of Error in Corrective Computerized Color Matching
Kazuo SANO and Hiromitsu ISHII

 It is generally known that you need at least one additional CCM correction to match a color so as to get the final sample
 degree of accuracy below ΔE*0.3 when the first matching accuracy is around ΔE*1, and at least two additional corrections when the first matching accuracy is around
ΔE*2. However, there has been no specific report on the accuracy of CCM matching from the theoretical standpoint until recently. In this report, we tried to set out the specific behavior of CCM corrections theoretically under ordinary conditions when the abnormal coloring factors are eliminated from the related parametersÅGPursuing more accurate CCM corrections there are five major factors that affect the CCM correction. The first is the calculation error stemming from the algorithm for the CCM corrective calculation (factor-A). The second is the error stemming from the deviation between the figures for the Kubelka-Munk theory and those for the actual ones (factor-B). The third is the error caused by production lots of the colorants (factor-C). The fourth is the error caused by coloring reproducibility (factor-D). And the fifth and final one is the error caused by the difference of the surface gloss of the matched samples (factor-E). As a result of our study, we have come to the conclusion that the errors caused by factors-A, B and C are negligibly small and the errors caused by factors-D and E would have direct effects on the degree of accuracy of CCM corrections. It is confirmed that provided you use colorants having good coloring reproducibility and you consider the reproduction of the surface gloss, it may be possible to obtain a final sample degree of ΔE*0.3 with one correction even under the condition of the first matching accuracy being around ΔE*2.

KEYWORDS : CCM, computer color matching, coloring, reproducibility