We show that reconstructing a hologram by its object beam leads to spa
tial filtering, namely, to the suppression of spatial frequency compon
ents that are perpendicular to the plane of the recording beams. We co
nduct experiments by rotating the transparencies of Ronchi gratings an
d crossed gratings and measuring the corresponding diffraction efficie
ncies. Good agreement is found with a theory based on image reconstruc
tion with a beam that does not quite satisfy the Bragg condition.