Study on correlation between the surround space constant of Retinex center/surround algorithm and images

Generally the surround space constant of Retinex´s center/surround algorithm is an empirical value that is between 25 and 250, and it is of small images. For the larger engineering images, how much should the parameter value be? In addition, in this algorithm, convolution is an operation whose efficiency is very low. It is a bottleneck that has impact on this algorithm´s application in image engineering. How to solve this problem will have impact on the algorithm´s application in the practical engineering.