A (k,n)-scalable secret image sharing (SSIS) scheme shares a secret image into n independent shadow images. This (k,n)-SSIS scheme can simultaneously provide the properties of threshold (k or more shadow images are required in reconstruction; but k − 1 or less shadow images reveal no information on the secret image) and the scalability (when k or more than k shadow images participate in reconstruction, more shadow images can reveal more information amount of secret image). In this paper, we deal with (k,n)-SSIS scheme with the smooth scalability such that the information amount of revealed image is “smoothly” proportional to the number of involved shadows, the whole secret image can be reconstructed only when all the n shadow images participate in reconstruction. Comparing with the existing smooth (k,n)-SSIS schemes, the proposed scheme has the less size of shadow image. Copyright © 2014 John Wiley & Sons, Ltd.