This communication deals with a prototype of a low- cost fish-eye camera developed by EDF R&D, meant to be an alternative for local and very short term solar forecasting to standard total sky imagers. The paper presents the results of a preliminary study demonstrating a very important pre-requisite for the use of fish-eye camera for solar forecasting purpose: the relationship between hemispheric sky images and the different components (global, diffuse and direct) of the surface solar irradiance (SSI). This study has been carried out with high quality "BSRN quality level" radiometric data and hemispheric sky images from a EDF R&D's test site on Reunion Island, in the Indian Ocean. This experimental study leads to very concluding and promising results on sub-hourly estimation of diffuse, direct and global SSI from sky images provided by the fish-eye camera.