Left: color–color diagram of the sources in the control field chosen for the 38.94-00.46 complex with photometric error σ < 0.03 mag. Extinction of A_V = 5 mag is indicated with an arrow. Center: the same for all sources in the control field, shown with a grayscale (and black contours) that indicates the density of points. The mean colors of these sources are marked with a green plus-sign. The red contours show the density of the sources that are in the foreground of the 38.94-00.46 complex. The contribution of these sources to the mean color is statistically subtracted from the mean, resulting in the mean color of the background sources, which is shown with a green cross. Right: frequency distribution of the extinction measurements toward individual sources () in a region where A_V > 6 mag. The small bump at slightly negative extinction values is produced by the foreground stars that are removed during the last step of the extinction mapping procedure (see Sect. 2.2). The surface density of the foreground sources identified in this way is also used in estimating the distances to the cloud complexes in Sect. 3.