CCD photometry of faint stars in the globular cluster M3 is presented. The observations reach down to V equal to about 23 mag, with a sample of approximately 5000 stars. The resulting color magnitude diagram has a turn-off significantly redder than those obtained in previous studies. Age and distance are derived by fitting the observed mean line to the theoretical isochrones by Chieffi and Straniero (1989). The dependence on the assumed metallicity and color excess values is studied in some detail. In general, theoretical and observed loci are in excellent agreement yielding (m-M)v from 14.85 to 14.93 mag) and t from 16 to 19 Gyr, depending on the different assumptions about reddening and metallicity. Finally, the luminosity function (LF) is presented. When incompletenesses are taken into account, the observed LF appears in good agreement with the curve predicted by theoretical models computed assuming a mass function with alpha = 2.5.