Analysis of image brightness distribution of a circumstellar disk at different evolutionary stages. The results for different evolutionary states are coded in colour. The shape of any mark denotes the region from whence it is taken. Vertical lines indicate resolution limits of selected interferometers. Horizontal lines give the ALMA sensitivity limit, the other two instruments do not have the required sensitivity. The flux is given in units of the total flux. Since this flux depends as well on ϵ, the sensitivity limit is affected. The dependence of the flux in regions B and C on ϵ is shown.