After the fundamental basics of leaf area index measurement by optical instrument and digital hemispherical photography were introduced, the impact of the camera exposures was analyzed for high quality fish-eye photo acquisition. We proposed a new method for camera settings. The optimum exposure would be two stops less exposure than the referenced exposure, which is measured by automatic exposure with the stands. This setting could be achieved by fixing the aperture and tuning the shuttle speed. The three bands of the photo were also compared to select the best one for sky-foliage segmentation. A digital photo processing procedure was proposed including selecting the blue band and using the area covering the 0~60° zenith angles for LAI calculation. Consistence was achieved between our results and those from LAI-2000 thanks to the multi-equipment comparison experiments on LAI measurement of Qinghai spruce.