Propagation of eigenmodes for beam transfer function uncertainty (left-hand panels) to an uncertainty in the lensing normalization (right-hand panels). The normalization eigenmodes are flat, with amplitudes given by approximately twice the beam uncertainty at the beam and noise cutoff scale (at ℓ ≈ 1000 for 100 GHz and ℓ ≈ 1500 for 143 and 217 GHz).