Levels of illumination and legibility

Technical Report · Tue Nov 01 04:00:00 EST 1977

OSTI ID:6606233

The visibility of tasks encountered in the working world ranges from easy to difficult to see objects. The assumption that experiments performed for threshold targets (difficult to see) can be extrapolated to higher contrast tasks (easy) was tested. The experiments indicate that threshold level studies should not be extrapolated to suprathreshold levels. The performance of the eye is not the same at the two levels. The threshold function is monotonic, that is, contrast required for detection decreases monotonically as luminance is increased, whereas the suprathreshold experiments result in a function with a minimum or optimum luminance level. Recommendations are made to expand the empirical base from which lighting level recommendations are derived to include the more commonly occurring situation involving visual task performance for suprathreshold tasks.

• Research Organization: National Bureau of Standards, Washington, DC (USA)
• OSTI ID: 6606233
• Report Number(s): PB-276531; NBSIR-77-1306
• Country of Publication: United States
• Language: English

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