Brightness level of the isophotes used to trace the small grain halo (see Sect. 3.2) drawn over semimajor axis a. Solid lines are used for the systems with inner perturbers and dashed lines for those with outer perturbers, and rows are used to show four different wavelengths that trace small halo grains: 2 µm, 10 µm, 21 µm, and 70 µm. The horizontal dashed lines denote the minimum surface brightness required to achieve a certain detection significance (S/N), denoted by a multiple of the noise, σ. Red lines are for an exposure time of t_exp = 1 h, blue for t_exp = 5 h. For the wavelength of 2 µm the corresponding instrument is JWST/NIRCam, for 10 µm and 21 µm it is JWST/MIRI, and for 70 µm it is Herschel/PACS.