We use narrow-band imaging (full width at half-maximum = 70 ??) to select a sample of emission-line galaxies between 0.20 a?? z a?? 1.22 in two fields covering 0.5 deg2. We use spectroscopic follow-up to select a subsample of HI?-emitting galaxies at z a?? 0.24 and determine the HI? luminosity function and star formation density at z a?? 0.24 for both of our fields. Corrections are made for imaging and spectroscopic incompleteness, extinction and interloper contamination on the basis of the spectroscopic data. When compared to each other, we find the field samples differ by I?I? = 0.2 in faint-end slope and I?log [L* (erg s-1)] = 0.2 in luminosity.