We examine the multifractal analysis of 2-dimensional black and white images. First, we created a multifractal image based on clasical algorithms, from which the MultiFractal Spectrum (MFS) can be calculated analytically. We study the influence of the percentage of black pixels in the results obtained by calculating the MFS based on the image obtained at different simulation steps. This point out the importance of statistical analysis on MFS when any scaling properties want to be studied, as for example multiscale porous media.