We measured changes in the color appearance of one light caused by another light presented in a w... more We measured changes in the color appearance of one light caused by another light presented in a well-separated region. Observers viewed a lo test field superimposed on a 3', 540 or 660 nm adapting field (32 or 320 td). The change in appearance due to noncontiguous light was determined by surrou~ing the 3O adapting field with a continguous 3O i.d., 5' o.d. ring of either 32 or 320 td. The ring was 540,660 nm or achromatic (tungsten-halogen "white"). The test was an admixture of 549 and 660 nm light, and varied from 6 to 1000 td. The observer adjusted the ratio of 549 to 660 nm test light so the test appeared neither reddish nor greenish. A 540 or 660 nm ring had a chromatic inducing effect on the small test that mimicked a simple surround contiguous with the test. Results with an achromatic ring were more complex: an isolated achromatic ring (no adapting field present) had virtually no effect on the color appearance of the test, but the same achromatic ring surrounding a chromatic adapting field shifted the test toward the color appearance of the adapting light (e.g. introducing a 'khite" ring surrounding a "green" adapting field shifted the test toward greenness). A thin ~nciI-width band of "white" light su~~rn~~ on a larger 5* adapting field had an effect similar to a "white" 3-5O ring. These results demonstrate (1) strong effects of the remote noncontiguous lights and (2) that the change in color appearance they cause is not a simple function of only the light in the noncontinguous region. The change depends on other lights in view. The visual processes revealed in these experiments are considered in terms of inferred illumination and surface reflectances of objects in natural scenes.
We study the amplitude of the weak gravitational lensing signal as a function of stellar mass aro... more We study the amplitude of the weak gravitational lensing signal as a function of stellar mass around a sample of relatively isolated galaxies. This selection of lenses simplifies the interpretation of the observations, which consist of data from the Red- sequence Cluster Survey and the Sloan Digital Sky Survey. We find that the amplitude of the lensing signal as a function of stellar mass is well described by a power law with a best fit slope \alpha= 0.74 \pm 0.08. This result is inconsistent with Modified Newtonian Dynamics, which predicts \alpha = 0.5 (we find \alpha > 0.5 with 99.7% confidence). As a related test, we determine the MOND mass-to-light ratio as a function of luminosity. Our results require dark matter for the most luminous galaxies (L >=10^11 L_sun). We rule out an extended halo of gas or active neutrinos as a way of reconciling our findings with MOND. Although we focus on a single alternative gravity model, we note that our results provide an important test for any alternative theory of gravity.
We measured changes in the color appearance of one light caused by another light presented in a w... more We measured changes in the color appearance of one light caused by another light presented in a well-separated region. Observers viewed a lo test field superimposed on a 3', 540 or 660 nm adapting field (32 or 320 td). The change in appearance due to noncontiguous light was determined by surrou~ing the 3O adapting field with a continguous 3O i.d., 5' o.d. ring of either 32 or 320 td. The ring was 540,660 nm or achromatic (tungsten-halogen "white"). The test was an admixture of 549 and 660 nm light, and varied from 6 to 1000 td. The observer adjusted the ratio of 549 to 660 nm test light so the test appeared neither reddish nor greenish. A 540 or 660 nm ring had a chromatic inducing effect on the small test that mimicked a simple surround contiguous with the test. Results with an achromatic ring were more complex: an isolated achromatic ring (no adapting field present) had virtually no effect on the color appearance of the test, but the same achromatic ring surrounding a chromatic adapting field shifted the test toward the color appearance of the adapting light (e.g. introducing a 'khite" ring surrounding a "green" adapting field shifted the test toward greenness). A thin ~nciI-width band of "white" light su~~rn~~ on a larger 5* adapting field had an effect similar to a "white" 3-5O ring. These results demonstrate (1) strong effects of the remote noncontiguous lights and (2) that the change in color appearance they cause is not a simple function of only the light in the noncontinguous region. The change depends on other lights in view. The visual processes revealed in these experiments are considered in terms of inferred illumination and surface reflectances of objects in natural scenes.
We study the amplitude of the weak gravitational lensing signal as a function of stellar mass aro... more We study the amplitude of the weak gravitational lensing signal as a function of stellar mass around a sample of relatively isolated galaxies. This selection of lenses simplifies the interpretation of the observations, which consist of data from the Red- sequence Cluster Survey and the Sloan Digital Sky Survey. We find that the amplitude of the lensing signal as a function of stellar mass is well described by a power law with a best fit slope \alpha= 0.74 \pm 0.08. This result is inconsistent with Modified Newtonian Dynamics, which predicts \alpha = 0.5 (we find \alpha > 0.5 with 99.7% confidence). As a related test, we determine the MOND mass-to-light ratio as a function of luminosity. Our results require dark matter for the most luminous galaxies (L >=10^11 L_sun). We rule out an extended halo of gas or active neutrinos as a way of reconciling our findings with MOND. Although we focus on a single alternative gravity model, we note that our results provide an important test for any alternative theory of gravity.
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