Relative distance error as function of distance in case of cosmological redshift (considers only expansion). Relative distance errors of 1, 2, and 3% are shown by horizontal dotted lines. For Cepheids, we adopt b = −3.26 (corresponds to the H-band Period–Wesenheit relation using F160W, F555W, and F814W in R+16), for Miras b₁ = −3.59, b₂ = −3.40, and log P_ref = 2.3 from Huang et al. (2018). If left uncorrected, RLB affects Cepheids at the 1% (2%) level for d >  62 Mpc (d >  123 Mpc). For Miras of mean log P_obs = 2.4, the 1% (2%) bias level is reached sooner, at d >  47.5 Mpc (d >  95 Mpc).