METHOD OF CALCULATING LUMINANCE

摘要

PROBLEM TO BE SOLVED: To provide a method of calculating luminance capable of extensively measuring the luminance distribution from a small number of photographed images, capable of easily changing the setting of photographing conditions corresponding to the distribution of luminance of an object for measurement even when using the digital still camera with narrow adjustment range of shutter speed. SOLUTION: The camera control part 2 sets the photographing condition of the camera 1 of the digital still camera 1. The image forming part 3 acquires a plurality of images photographed in different photographing conditions from the camera 1, converts the pixel value of each pixel regarding each image into the luminance by using the following conversion formula, then combines the results for obtaining the luminance distribution of the object to be measured. Herein, if the relation between the pixel value and the luminance of the camera 1 can be represented by the ogive function, the luminance Y is expressed as follows: Y=exp((X-2A+2B×ln(f))/C)/SS, where the shutter speed of the camera 1: SS, the F value of stop: f, the pixel value: X, and the constant depending on the camera 1: A, B and C, where 0