Sky View Factors from High-Resolution Scanned Fish-eye Lens Photographic Negatives

Abstract

A computerized method for calculating the sky view factor from fish-eye lens photographic negatives is presented. The images are scanned and stored on CD ROM, each CD holding 100 images. The images can be retrieved at very high resolutions of up to 2048 × 3072 pixels for one 24 mm × 36 mm negative. The calculations include corrections for lens projection distortion and restrictions in field of view. They are compared to standard methods of calculating the sky view factor. For applications of the sky view factor where the effective infrared radiation is of interest, a method to account for zenith angular variation in atmospheric transmissivity to infrared radiation is presented.