Error in BC (top panels) and luminosity (bottom panels) caused by fixing carbon, alpha, and metallicity at zero for stars with log g < 3.6. The values BC_G and L were calculated with all three parameters taken into account, and the “mod.” (modified) values show the effect when one or several of the parameters - [M/H], [α/M], and [C/M] - are fixed to zero. The value N denotes the number of stars for BC.