Relationship between warm corona parameters and optical derived parameter measurements. Top: relationship between Eddington ratio and hot corona photon index, shown for all sources with soft excesses. The best fit line and errors are shown by the shaded purple region. Correlations between these parameters found in previous works are shown in black lines of various line styles. Middle: Same as top, but for the warm corona photon index. Bottom: relationship between black hole mass and warm corona temperature, kT.