Temporally averaged histograms of the (bolometric) intensity (solid lines) for various stellar parameters (the bin-size is 100). To ease comparisons between the different stellar parameters, we normalized the individual intensity scales with its mean value. Furthermore, we have indicated the respective FWHM of the intensity histograms, I_FWHM, (dotted lines), a measure of the intensity contrast. Note the different ordinate scale in the top panel. The bimodal distributions are given due to the asymmetry and the large contrast in the up and downflows.