Based on the high dynamic range (HDR) image technology, a calculation method for obtaining the luminance parameters is investigated. In this method, according to the photographic characteristics and the imaging principle of digital cameras, a set of low dynamic range time series images is synthesized into a HDR image using the Photosphere software. The gray value of this image is calculated and fitted with the tristimulus value of R, G, B data obtained by linear transformation. And thus the luminance is obtained. The luminance of each color block in the standard color plate is calculated under three background luminance and it is found that the average luminance error is less than 9.22%. Moreover, the luminance errors of all color block targets and coloured targets are reduced with the decrease of background luminance, and the luminance error of the gray targets reaches a minimum when the background luminance is within an appropriate scope.