Evaluation of flash and fluorescent sources with respect to recommended ocular exposure thresholds

A system was established for the evaluation of sources of optical radiation with respect to recommended ocular exposure limits. This system consists of a diode array radiometer calibrated for absolute radiometric measurements and software for the application of the currently accepted threshold limits for exposure to the various wavelengths of radiation. Absolute calibration of the array radiometer was accomplished to within 3 percent of values obtained by a conventional instrument. Day-to-day repeatability of the instrument indicates the possiblility of absolute calibration of the detector array responsivity for everyday use in the measurement of continuous sources to an accuracy of plus-or-minus 2.8 percent. It was also determined that the output of several optical sources used in copying machines and photography can exceed the retinal thermal Threshold Limit Value. One typical 35 mm photographic flash exceeded the threshold at a range of 3 meters. Other threshold expressions were not exceeded at significant distances or exposure durations for these sources

A victory for equivalent background — on average

A psychophysical experiment was carried out to examine the relationship between image contrast and overall perceived brightness. A second phase of the experiment looked at the relationship between the perceived brightness of variegated backgrounds and the simultaneous contrast effect produced by such backgrounds. These results have important ramifications for procedures used to calculate adapting chromaticities and luminances for image displays. The results suggest that the traditional concepts of linear luminance integration and equivalent background are satisfactory on average. However, results for individual observers show very striking, consistent, and significant trends with substantial inter-observer variability. These results help to reconcile differences between fundamental vision science experiments and practical experiences with color appearance models

Modeling Observer Metamerism through Monte Carlo Simulation (Poster)

Metameric color matches depend on the observer’s color matching functions. Data were collected on observer variability in typical metameric matches. A Monte Carlo simulation, using a model of color matching functions and physiological data, was performed to derive a complete colorimetric system capable of predicting inter-observer variability in addition to mean color matches

The ZLAB Color Appearance Model for Practical Image Reproduction Applications

At its May, 1997 meeting in Kyoto, CIE TC1-34 considered 4 proposed color appearance models for adoption as the CIECAM97s model. The ZLAB model was one of those considered. Although it was rejected by TC1-34 because of its simplicity, there are many situations (such as typical crossmedia image reproduction) for which a more complex model might not be necessary, or even useful. Thus, the ZLAB model is being published as a simpler alternative to CIECAM97s that retains many of its positive features

Refinement of the RLAB Color Space

The prediction of color appearance using the RLAB color space has been tested for a variety of viewing conditions and stimulus types. These tests have shown that RLAB performs well for complex stimuli and not-so-well for simple stimuli. This article reviews the various psychophysical results, interprets their differences, and describes evolutionary enhancements to the RLAB model that simplify it and improve its performance