Rest-frame 1 μm half-light radius for SMGs (red circles), less massive field galaxies (grey dots) and massive field galaxies (black stars) as a function of (a) redshift and (b) stellar mass. In each panel, we show a running median for SMGs (dashed blue line), field galaxies (dashed grey line) and massive field galaxies (dashed black line) as well as a representative uncertainty. We identify a consistent reduction in rest-frame 1 μm size with increasing redshift in both field samples and the SMG sample, as well as a consistent mass-size relation compared to that seen in Fig. 6. This indicates that the morphology variation with wavelength identified in both field samples and the SMGs in Fig. 8 is not driven by K-correction effects.