FWHM in each filter, as measured in PSFs made with commissioning data. Each dot is the FWHM average in x and y directions from 2D Airy fits of the PSF images in each MIRI filter. The pixel size is 0.11″, and light grey dashed lines materialise the pixels. The telescope diffraction limit is indicated by the black dashed line. The excess with respect to the diffraction limit at 5.6 and 7.7 µm is due to the broadening of the PSF induced by the diffraction and scattering in the detector substrate (see Sect. 4.3).