ALMA observations of dust continuum emission for SR 21 (top panels) and HD 135344B (bottom panels). The left columns show the Band 9 (689 GHz) and Band 7 (336 GHz) continuum, with the contour overlaid at 10, 20, ..., 90% of the peak. The third column shows the overlay of the contours with a step of 20% of the peak (black is Band 9, red is Band 7). The right column shows the resolved α_mm in colour contours. The beam size is indicated in each plot.