Recently, two novel techniques for the extraction of the phase-shift map (Tomassini et al. (2001). Applied Optics40, 35) and the electronic density map estimation (Tomassini P. & Giulietti A. (2001). Optics Communication199, 143–148) have been proposed. In this article, we apply both methods to a sample laser–plasma interferogram obtained with femtoseconds probe pulse, in an experimental setup devoted to laser particle acceleration studies.