Use of a digital camera as a sky luminance scanner
We are living in an age where digital photography is in full bloom. Even day, there are cheaper and more powerful digital cameras put to the market. Some of them can be fitted with a fish-eye lens so that their image covers the entire field of view. Previous studies (Dumortier, 2005) have shown that once calibrated in luminance, a digital camera was an accurate and useful tool to characterize the luminance distribution of indoor scenes. Could we also use digital cameras to describe the luminance distribution of the sky vault? This is what we tested in this study.From May 2005 to December 2005, we installed an EKO sky luminance scanner at the IDMP station of ENTPE, in Vaulx-en-Velin, France. The scanner measured 145 luminances over the entire sky, from sunrise to sunset, every 10 minutes. For some days, at the time of the scanner measurements, we took images of the sky vault with a luminance calibrated digital camera. This was a Nikon Coolpix 5000 with a fish-eye lens Nikon FCE8. The images were then processed to produce 145 luminances equivalent to the ones of the scanner. The comparison shows a root mean square error less than 15％ between the camera and the scanner. The camera offers much higher spatial and temporal resolutions than the scanner. However, for continuous operation, the CCD pixels directly struck by sunlight could burn; the camera should therefore be shaded by a disk. Replacing the compact camera by a single lens reflex camera could solve the problem.
sky luminance distribution sky scanner digital camera fish-eye lens calibration
Matej B. Kobav Dominique Dumortier
University of Ljubljana, Slovenia DGCB-LASH Lyon, France
国际会议
26th Session of the CIE(国际照明委员会（CIE）第26届大会)
北京
英文
410-413
2007-07-04（万方平台首次上网日期，不代表论文的发表时间）