Table I
Reflectances of non-selective samples on non-selective grounds found to appear black, gray, and white.
Background reflectance | Black | Lightness quality Gray | White |
---|
0.037 | 0.037 | 0.037–0.377 | 0.377–0.803 |
0.230 | 0.037–0.042 | 0.042–0.430 | 0.430–0.803 |
0.803 | 0.037–0.084 | 0.084–0.630 | 0.630–0.803 |
Table II
Effect of intensity of stimulus, reflectance of background, and depth of shadow on lightness compensation. (W°, degrees white in shadowed disk; S°, degrees white in brightly illuminated disk; F.C., apparent footcandles; Ratio, brightly illuminated to shadowed F.C.) Reflectance of white used for background and in disks=0.80. Reflectance of black used for background and in disks=0.03. Reflectance of gray background=0.26.
| | White background | Gray background | Black background |
---|
W° | F.C. | S° | F.C. | Ratio | S° | F.C. | Ratio | S° | F.C. | Ratio |
---|
A |
Bright illuminance=16.15 ft.-c |
Shadowed illuminance=0.879 ft.-c |
360 | 0.703 | 322.7 | 11.63 | 16.54 | 208.7 | 7.75 | 11.02 | 184.0 | 6.78 | 9.46 |
270 | .536 | 252.0 | 9.20 | 17.16 | 177.3 | 6.62 | 12.35 | 152.3 | 5.81 | 10.84 |
180 | .360 | 168.3 | 6.30 | 17.50 | 142.0 | 5.33 | 14.80 | 123.7 | 4.68 | 13.00 |
90 | .193 | 74.3 | 3.07 | 15.91 | 84.3 | 3.39 | 17.56 | 60.3 | 2.58 | 13.37 |
45 | .114 | 33.3 | 1.61 | 14.12 | 43.5 | 1.94 | 17.02 | 31.3 | 1.61 | 14.12 |
0 or 15 | .026 | 3.5 | 0.65 | 25.00 | 1.0 | 0.48 | 18.46 | 10.8 | 0.81 | 15.58 |
B |
Bright illuminance=16.15 ft.-c |
Shadowed illuminance=0.388 ft.-c |
360 | 0.310 | 302.7 | 10.98 | 35.42 | 178.3 | 6.62 | 21.35 | 126.7 | 4.84 | 15.61 |
270 | .237 | 236.3 | 8.56 | 36.19 | 155.3 | 5.81 | 24.51 | 104.3 | 4.04 | 17.05 |
180 | .160 | 156.3 | 5.81 | 36.31 | 126.0 | 4.84 | 30.25 | 85.0 | 3.39 | 21.19 |
90 | .085 | 70.0 | 2.91 | 34.23 | 74.0 | 3.07 | 36.12 | 47.7 | 2.10 | 24.71 |
45 | .050 | 31.0 | 1.61 | 32.20 | 38.3 | 1.78 | 35.60 | 22.0 | 1.29 | 25.80 |
0 or 15 | .012 | 8.2 | 0.81 | 67.50 | 0.5 | 0.48 | 40.00 | 7.2 | 0.65 | 28.26 |
C |
Bright illuminance=16.15 ft.-c |
Shadowed illuminance=0.009 ft.-c |
360 | 0.0072 | 92.3 | 3.71 | 515.3 | 67.7 | 2.74 | 380.5 | 36.7 | 1.78 | 247.2 |
270 | .0055 | 71.7 | 2.91 | 529.1 | 53.3 | 2.26 | 410.9 | 26.2 | 1.45 | 263.6 |
180 | .0037 | 47.3 | 2.10 | 567.6 | 37.0 | 1.78 | 481.1 | 16.8 | 1.13 | 305.4 |
90 | .0020 | 35.5 | 1.78 | 890.0 | 24.7 | 1.29 | 645.0 | 7.2 | 0.65 | 325.0 |
45 | .0011 | 25.7 | 1.29 | 1172.7 | 12.8 | 0.97 | 881.8 | | | |
0 | .0003 | 17.3 | 1.13 | 3766.7 | 5.0 | 0.65 | 2166.7 | | | |
Table III
Effect of a divided background. Illuminance on brightly illuminated side=16.15 app. ft.-c. Illuminance on shadowed side=0.879 app. ft.-c. Reflectance of white background = 0.80. Reflectance of black background=0.03. (W°, degrees white in shadowed disk; S°, degrees white in illuminated disk matching the shadowed disk; App. ft.-c, apparent footcandles; Ratio, luminance of illuminated disk to luminance of shadowed disk.)
A |
---|
Shadowed white background and illuminated black background |
---|
Shadowed white background | Illuminated black background | |
---|
W° | App. ft.-c | S° | App. ft.-c | Ratio |
---|
360 | 0.703 | 127.7 | 4.84 | 6.88 |
270 | .536 | 88.0 | 3.55 | 6.62 |
180 | .360 | 51.0 | 2.26 | 6.28 |
90 | .193 | 11.8 | 0.81 | 4.20 |
45 | .114 | 2.5 | 0.48 | 4.21 |
|
B |
Shadowed black background and illuminated white background |
Shadowed black background | Illuminated white background | |
W° | App. ft.-c | S° | App. ft.-c | Ratio |
|
360 | 0.703 | 360.0 | 12.92 | 18.38 |
270 | .536 | 334.3 | 11.95 | 22.29 |
180 | .360 | 299.0 | 10.82 | 30.05 |
90 | .193 | 223.3 | 8.24 | 42.69 |
45 | .114 | 135.0 | 5.17 | 45.35 |
0 | .026 | 21.3 | 1.13 | 43.46 |