Ca ii  H contrast as a function of the parameters of convection. Left panel: contrast as a function of the amplitude of convective motions at the bottom photosphere. Middle panel: contrast as a function of height where convective velocities change their sign. Each point represents an average value over a bin that contains an equal number of data points on the abscissa axis. The uncertainty σ is measured as a standard deviation between the average and the individual values for each bin and then averaged for all bins. Right panel: bi-dimensional representation of the Ca ii  H contrast as a function of parameter of convection. Each color rectangle in the scatter plot indicates the mean value of the contrast for a given range of convective velocity and height of sign reversal. The white areas are the locations where a particular combination of convective velocities and reversal heights is not present in our data.