A new photometric metal abundance and luminosity calibration for field G and K giants.

Photometry of 260 G and K giants, using a fast broad-intermediate band photometric system (UB Viyz system) is used to calibrate chemical composition, [Fe/H], luminosity, Mv and colour excess, E(B-V). A single S-20 surface photomultiplier is used. The UB Vi photometry is transformed to be on the Johnson UBVRI system. Calibrations applicable to the ranges 040<R-i<065 (G2-K3), o6 <R-i<090 (K3-K5) are given. A photometric luminosity index, Mv(yz), is derived for which Ims errors are t I mag. Several indices are calibrated for chemical composition, [Fe/H], and typical rms errors of j in [Fe/H] are obtained for stars of known colour excess, E(B-V). For stars of unknown colour excess, E(B-V) is determined with an rms error of j and [Fe/H] with an rms error of + . For stars with Mv< -I, the errors are larger.