— This paper supplies chromaticity coordinates and relative luminances of certain natural surfaces for which spectral reflectance distributions are presently available. Modelers of geographical databases for simulator displays may use this information to guide color selection for scene components. Where the reflectance data permit, relative luminances have also been computed for simulation of landscapes viewed through night‐vision devices.

The time course of recovery of spatial resolution following adaptation to a uniform field was measured for test probes presented at lower illuminance than the adapting field. Six observers were tested in a Maxwellian-view system using 20 degrees adapting fields of 1.6-2.6 log photopic trolands. Test stimuli were 7 degrees, 250 ms Gabor patches (1 and 6 cpd) of mean retinal illuminance 2-3 log units lower than the adapting field. During the 9 s after adapting field offset, contrast thresholds for orientation discrimination followed an exponential-decay function and showed longer recovery times for larger illuminance decrements and higher spatial frequency.

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