Relation between τ(250 μm) and τ(J) in the field G95.76+8.17. The black solid line is a linear weighted total least-squares fit to all data points. The blue and red points and lines of the corresponding colour show the data and the fits below and above the threshold of τ(J) = 0.6, the dashed line indicates the division. The values of the slopes k are given in the plot. Error bars are shown for a set of random data points.