Herschel opens a large field of investigations on the hidden star formation in galaxies. Combining UV and far-IR rest-frame data allows us to measure all the star formation in galaxies and to estimate the net dust attenuation. The analysis can be performed from the local universe using far-IR and GALEX surveys to high z (up to z < 2) by combining deep U data with the Herschel observations of the HerMES project.
The calibration of dust attenuation, and then star formation rate, is reinvestigated. We present the results of the first analyses performed with Herschel data obtained in the Lockman and COSMOS fields as part of the HerMES project and discuss the reliability of dust attenuation corrections.