We report the results of J -band infrared spectroscopy of a sample of 13 z = 1 field galaxies drawn from the Canada-France Redshift Survey , targeting galaxies whose redshifts place the rest frame H \alpha line emission from HII regions in between the bright night sky OH lines .
As a result we detect emission down to a flux limit of \simeq 10 ^ { -16 } ergs cm ^ { -2 } s ^ { -1 } corresponding to a luminosity limit of \simeq 10 ^ { 41 } ergs at this redshift for a H _ { 0 } = 50 km s ^ { -1 } Mpc , ^ { -1 } q _ { 0 } = 0.5 cosmology .
From these luminosities we derive estimates of the star-formation rates in these galaxies which are independent of previous estimates based upon their rest-frame ultraviolet ( 2800Å ) luminosity .
The mean star-formation rate at z = 1 , from this sample , is found to be at least three times as high as the ultraviolet estimates .
The dust extinction in these galaxies is inferred to be moderate , for standard extinction laws , with a typical A _ { V } = 0.5 –1.0 mags , comparable to local field galaxies .
This suggests that the bulk of star-formation is not heavily obscured , unless one uses greyer extinction laws .

Star-forming galaxies have the bluest colours and a preponderance of disturbed/interacting morphologies .
We also investigate the effects of particular star-formation histories , in particular the role of bursts vs continuous star-formation in changing the detailed distribution of UV to H \alpha emission .
Generally we find that models dominated by short , overlapping , bursts at typically 0.2 Gyr intervals provide a better model for the data than a constant rate of star-formation .
The star-formation history of the Universe from Balmer lines is compiled and found to be typically 2–3 \times higher than that inferred from the UV at all redshifts .
It can not yet be clearly established whether the star-formation rate falls off or remains constant at high-redshift .