Transfer functions at 250 μm (with a FWHM of 18″) binned as a function of signal-to-noise ratio (S/N) where the noise standard deviation σ_HF is from a simulation including only white and high-frequency noise. The red curve and red shaded area show the cumulative fraction of the flux that is recovered and the associated uncertainties, from the lower S/N limit (3σ_HF for NGC 2146 and 2σ_HF for NGC 2976) up to the maximum of the current S/N bin.