a) Frequency sweep (“local sweep”) for four resonators, of which the last two are very close together. b) Phase response of a tone placed at MKID 171 to the position of a point source at the image plane of the chip outside the cryostat; we see a single beam response. c) Phase response of a tone placed at MKID 172 to the position of a point source at the image plane of the chip outside the cryostat; we see a response of the pixel itself and a −10-dB response at the spatial position of MKID 173. d) Measured (blue squares) and modelled crosstalk (red dots) together with a simple model calculation (dashed line) as guide to the eye. e) Estimated crosstalk for the array under dark and cold conditions obtained from a model calculation based upon the data presented in Fig. 3a.