Standard deviation of quiet Sun (⟨B_l⟩/μ ≤ 10G) intensity at continuum, σ_IC,QS (red) and line core, σ_IL,QS (blue) as a function of μ. The dotted lines represents the linear fit to σ_IC,QS and σ_IL,QS over the range 0.3 ≤ μ ≤ 1.0 (largely hidden due to the close agreement), extrapolated to μ = 0. The dashed line denotes the threshold (μ = 0.1) below which pixels were excluded from the rest of the study in view of the scatter in measured intensity.