Spectral energy distribution incident on HST/WFC3 filters F555W (yellow) and F814W (black) for a typical TRGB star (left) and a 10-day Cepheid (right). Un-reddened spectra at rest are plotted in dark blue and the un-reddened spectra at z = 0.025 in cyan. Spectra reddened by E(B − V) = 0.10 mag are shown at rest (red) and at z = 0.025 (magenta) for illustration purposes. The sensitivity of stars near the TRGB observed in F814W to even light reddening and small redshift is readily apparent and mirrors that of 10 d Cepheids observed in F555W.