By selecting the JPCam filters appropriately, several stellar parameters observed in J-PAS should be measurable, such as effective temperature, surface gravity, iron abundance, and α/Fe.

The photometric data obtained by J-PAS reproduce the spectral energy distribution (SED) of the stars. The determination of these spectral parameters can be carried out through the comparison between the observed and theoretical SEDs, calculated for a large interval of spectral parameters. Some characteristics of the SEDs, such as the Balmer jump (~3647A) and the slope of the Paschen continuum (between 3800A and 8200A), that are sensitive to to the stellar parameters, will be used as primary indicators of these parameters. An analysis of a large sample of the Galactic Halo stars, will also allow us to accurately determine the density and metallicity profiles of old and metal-poor stars in the Galaxy.