Luminance gradient for evaluating lighting

Abstract

This paper introduces luminance gradient as a metric for evaluating common non-uniform luminous environments. Luminance gradient is defined as the largest change rate and the polarity of spatial luminance variation on a large surface or across the entire field of view in high resolution. The metric, a visualization method, and a freely available MatLab code for plotting luminance gradient maps have been developed. The retinal resolution of pixels for mapping luminance gradient has also been identified. A camera-aided measurement method of luminance gradient is proposed, which is demonstrated in two case studies of the evaluation of different types of luminous environments. Moreover, this study explored whether luminance gradient could also be obtained from computer simulations using lighting software programs AGI32 and HeliosPro.

Matrycowe pomiary luminancji elektroluminescencyjnych źródeł światła i opraw oświetleniowych -; stan techniki

“…High Dynamic Range). Związek wyników pomiarów w odniesieniu do aparatu wzroku człowieka jest jednak zbyt rzadko dostrzegany [14] i najczęściej nie jest wystarczająco eksponowany. Zdaniem autora artykułu, aby jednoznacznie rozwiązać problem wiarygodności wyników pomiarów, w pierwszej kolejności należy przybliżyć obecnie wykorzystywane technologie, przeprowadzając analizę możliwości pomiarowych, obliczeniowych i kalibracyjnych istniejących urządzeń.…”

Control and evaluation of room interior lighting using digital camera as the sensor

“…To use camera as a sensor for luminance measurement, a camera has to be calibrated by any one of the methods available. Calibrations of raw HDR images can be done in the following ways [2]: 1)Vignetting correction ii) Photometric calibration using a calibration factor (CF).Based on the conversion factor method the relation of actual and scene luminance value is obtained here. To obtain the CF integrating sphere or selection of calibration curve for minimum error using color checker chart method can be taken.…”

“…For color surfaces the average error can be form 9.3 % to 13.1%. High Dynamic Range photography help to measure and interpret the spatiotemporal distribution of luminance in line with visual perception [2]. Newsham G R and Arsenault C D [3] demonstrated that a single Complementary Metal Oxide Semiconductor (CMOS) camera chip can replace the multiple sensors required by conventional systems for daylight harvesting, shading control and occupancy sensing.…”

“…The tools used is Nikon Coolpix 5400 digital camera with a fisheye lens (Nikon FC-E9) with a tripod for the HDRI luminance measurement and Minolta LS110 for the reference luminance measurements [1]. Camera-aided imaging method for lighting application is suggested by Cai [2] : Conventional light meters are not suitable for measurement of uniformity if the light distribution is not the same. This difficulty can be overcame by the usage of digital camera.…”

“…Day light harvesting is much less successful popular lighting control strategy. Lighting represents 17.5% to 34.2% of all electrical consumption in commercial buildings [2] . So the reduction of this is one of the basic need nowadays.…”