Brightness Of Surfaces Research Articles

Specularity, brightness, achromatic color--and orthogonality.

For objects under the same illumination, the more specular object appeared brighter. This occurred irrespective of an object’s apparent achromatic color, the distance at which it was viewed, the level of illumination, the method used for collecting observations, and other conditions. Also, when identical specular objects were differently illuminated, the one under the higher illumination, with the higher maximal luminances, appeared brighter. In the five experiments, which involved 340 subjects subdivided into 17 groups, large fields of view and real spaces were used. The results supported the conclusion that apparent brightness and achromatic color are orthogonal phenomena, and that in four of these experiments increased apparent brightness was correlated to, if not determined by, maximal specular luminances without regard to achromatic colors and diffuse luminances. This conclusion was necessarily modified by a fifth experiment, which showed that if placed under sufficiently high levels of illumination, less specular surfaces appeared brighter than more specular surfaces. This was taken to mean that a total account of the apparent brightness of surfaces would depend on an undiscovered algorithm involving maximal specular and diffuseluminances and their areal extents. With regard to the validity of the studies, the subjects were shown to have phenomenally discriminated brightness from glossiness and glare. Finally, phenomenal gloss and glare were found to be correlated to a surface’s level of specularity.

各種ステンレス鋼の光輝性に及ぼす真空加熱条件の影響について

各種ステンレス鋼の光輝性に及ぼす真空加熱条件の影響について

Photometric studies of diffusely reflecting surfaces with applications to the brightness of the Moon

Diffusely reflecting surfaces for simulating brightness of lunar surfaces, noting pronounced rise of reflectivity at small phase angles

The Non-Additivity of Heterochromatic Brightnesses

Although standard practice in up-to-date photometric laboratories shows that the expert is well acquainted with the intricacies of visual heterochromatic photometry, several recent publications on the non-additivity of heterochromatic brightnesses seem to indicate that the basic problems involved are not always fully understood by non-specialist photometrists. In this paper the author reviews the results of three independent investigations which all show that there is a definite, although non-linear relationship between the apparent brightness of surfaces of different colour and the photometric assessment of their brightness in terms of luminance as defined by the C.I.E. The general trend of this non-linear relationship between brightness and luminance is revealed and discussed. Finally, some suggestions are made how heterochromatic brightnesses can best be assessed visually in terms of their luminances.

The spectral sensitivity of the fovea and extrafovea in the Purkinje range

The spectral sen sitivity of the retina has been measured by finding the energy required at various wave-lengths through the visible spectrum to match the brightness of a fixed comparison field. Results are recorded for two observers for a series of brightness levels within the Purkinje range and for three retinal areas, the fovea, 3° from th e fovea an d 10° from the fovea. A small shift of the foveal luminosity curve to wards shorter wave-lengths has been observed with decreased brightness of the matching field, accompanied by the development of a hump on the red side of the curve. This may be due to the progressive isolation of the red response at low intensities. Forth e extrafoveal areas, the usual Purkinje shift was observed, although surprisingly high intensities were required before the photopic curve was approached. This suggests that the rods may continue to function over a greater range of intensities than is generally accepted. No sudden change from rod to cone vision was recorded, incontrast to other visual functions, an d of the possible mechanisms by which the transition from one system to the other may operate, the special tendency of the rod response towards convergence an d summation at low intensities seems the most likely. Approximate solutions to problem s in p h o to m e try concerned with the change in relative brightness of coloured surfaces with reduced illumination may be derived by comparison with the corresponding changes which occur between monochromatic radiations of the same hue.

Apparatus and Method for the Photographic Measurement of the Brightness of Surfaces

Apparatus and Method for the Photographic Measurement of the Brightness of Surfaces