The use of Schmidt Telescopes for the determination of space density gradients is discussed. Space densities can be determined by a three colour photometry for main sequence stars with M< 8. 0 and later type giants of population I and for metal poor stars in higher galactic latitudes with M< 7. 0. A general synthesis of the present available results is not yet possible. But the determination of a density gradient for later type giants along a galactic radius, the distribution of metal poor stars in a galactic meridian and around the galactic centre seems to be possible with the existing observational material.