Photometric calibration of zoom lens systems

Abstract

This paper describes a calibration method of zoom lens systems to eliminate the photometric distortion due to vignetting. A novel camera model including the variable cone is proposed to account for the marginal intensity reduction observed in images. Using the theoretical model, we first show that the serious distortion due to vignetting appears when using a zoom lens that has open aperture and long focal length. Then we present the calibration method to estimate the intensity reduction from the lens parameters of zoom and iris. The experimental results demonstrate the validity of our theoretical model and the effectiveness of the photometric calibration of zoom lens systems.