The paper is devoted to the study of the underlying stellar population of a sample of 62 nearby early-type galaxies, predominantly located in low density environments, a large fraction of which showing emission lines. Ages, metallicities and [{alpha}/Fe] ratios have been derived through the comparison of Lick indices measured at different galacto-centric distances (7 apertures and 4 gradients) with new Simple Stellar Population (SSP) models which account for the presence of alpha/Fe-enhancement. The SSPs cover a wide range of ages (10^8^-16x10^9^yr), metallicities (0.0004<=Z<=0.05) and [{alpha}/Fe] ratios (0-0.8). To derive the stellar population parameters we use an algorithm that provides, together with the most likely solution in the (age, Z, [{alpha}/Fe]) space, also the probability density function along the age-metallicity degeneracy. We derive a large spread in age, with SSP-equivalent ages ranging from a few to 15Gyrs. Age does not show any significant trend with central velocity dispersion sigma_c_ but E galaxies appear on average older than lenticulars.