Example of source injection. The model of diffuse emission between a pair of simulated galaxy clusters (masked within their R₂₀₀; green dashed circles) found in the simulation with B₀ = 0.1 nG (lower left panel) is multiplied by a factor f_B = 1, 10², 10⁴ imaged and masked after being injected into the source-subtracted sky visibilities (upper left, upper central, and upper right panels, respectively), or it is injected through the image-plane (lower centre and lower right panels for f_B = 10² and 10⁴, respectively). The image with f_B = 1 in the upper left panel, due to the very low brightness of the model with B₀ = 0.1 nG, is equal to the source-subtracted sky image Im_empty, where the only features are the residuals from the source subtraction process that fall outside the masks. The white contours are set to 5 times the rms value in Im_empty.