Dependence of the SFR(UV) calibration on metallicity and IMF. Shown is the SFR per unit UV luminosity at 1500 Å in units of M_⊙ yr^-1 per (erg s^-1 Å^-1) on the left y-axis, or in M_⊙ yr^-1 per (erg s^-1 Hz^-1) on the right y-axis. Same symbols and colours as in previous figures (cf. Table 1). These values assume constant SF over 1 Gyr. The dotted horizontal line show the value of the Kennicutt (1998) SFR(UV) calibration rescaled to a Salpeter IMF with M_low = 1   M_⊙ for comparison. Above/below this line the SFR deduced from the UV luminosity is higher/lower.