Mass-luminosity relation using L from Sect. 3.1 and ℳ_ℳ−R from Sect. 3.4. The metallicities are color coded as indicated. For comparison we plot isochrones for 0.2, 2, and 13 Gyr (dashed lines in increasingly darker green) from BHAC15. The red solid line indicates the fit we obtained in Eq. (10) Obvious outliers, and stars discussed in reference to this figure in Sect. 5.2, are encircled: #4=GJ 1235 (J19216+208), #7=RX J0447.2+2038 (J04472+206), #8=1RXS J050156.7+010845 (J05019+011), #10=G 234-057 (J09133+688), #11=TYC 3529-1437-1 (J18174+483), #12=StKM 2-809 (J12156+526), and #14=K2-33 (J16102−193).