In the low temperature regime (T<0.3T(m)), the microstructure of sputtered films is determined predominantly by the mechanisms of self-shadowing. Shadowing effects are directly related to the angular distribution of incoming sputtered particles. The angular distributions of copper and lead particles sputtered by Ar+ ions in a planar magnetron geometry were measured using a differentially pumped pinhole camera. The pressure in the pinhole camera was lower by a factor of 10 compared to the ambient working gas. Thus it was possible to monitor the angular distribution of the incoming sputter particles for working gas pressures up to 4 Pa. Transparent films of the impinging particles were deposited on semicircular transparent substrates. Their relative thicknesses were measured by optical densitometry, giving a direct representation of the angular distribution at aa arbitrarily chosen point of the sputter chamber. A comparison of the measured angular distributions with distributions calculated for the particular geometry of the experimental setup under neglection of gas phase scattering shows that for low gas pressures, the angular distribution is determined mainly by the shape of the target erosion zone, which implies a significant deviation from isotropy. Increasing the gas pressure leads to a broadening of the angular distributions towards isotropy of particle incidence. Nonetheless, the geometry of the erosion zone still has a measurable influence on the shape of the distribution.