Context : We present new H \alpha + [ NII ] imaging data of late-type galaxies in the Herschel Reference Sample aimed at studying the star formation properties of a K-band-selected , volume-limited sample of nearby galaxies .
The H \alpha + [ NII ] data are corrected for [ NII ] contamination and dust attenuation using different recipes based on the Balmer decrement and the 24 \mu m luminosities .
We show that the H \alpha luminosities derived with different corrections give consistent results only whenever the the uncertainty on the estimate of the Balmer decrement is \sigma [ C ( H \beta ) ] \leq 0.1 .
We use these data to derive the star formation rate of the late-type galaxies of the sample , and compare these estimates to those determined using independent monochromatic tracers ( FUV , radio continuum ) or the output of spectral energy distribution ( SED ) fitting codes .
This comparison suggests that the 24 \mu m based dust extinction correction for the H \alpha data might be non universal , and that it should be used with caution in all objects with a low star formation activity , where dust heating can be dominated by the old stellar population .
Furthermore , because of the sudden truncation of the star formation activity of cluster galaxies occurring after their interaction with the surrounding environment , the stationarity conditions required to transform monochromatic fluxes into star formation rates might not always be satisfied in tracers other than the H \alpha luminosity .
In a similar way , the parametrisation of the star formation history generally used in SED fitting codes might not be adequate for these recently interacting systems .
We then use the derived star formation rates to study the SFR luminosity distribution and the typical scaling relations of the late-type galaxies of the HRS .
We observe a systematic decrease of the specific star formation rate with increasing stellar mass , stellar mass surface density , and metallicity .
We also observe an increase of the asymmetry and smoothness parameters measured in the H \alpha -band with increasing SSFR , probably induced by an increase of the contribution of giant HII regions to the H \alpha luminosity function in star-forming low-luminosity galaxies .

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