Pearson correlation coefficient (ρ), absolute difference between the slop and unity (|slop − 1|), and scatter (σ) between asymmetry calculated using Eq. (28) and A_noise-free as a function of f₁ and f₂. The values are color-encoded using histogram equalization scale. The black circle marks the optimal f₁ = 2.25 and f₂ = 2.1 we determine empirically, while the red triangle marks the f₁ = 1 and , as suggested in Wen & Zheng (2016).