We report on a new digital signal processing technique that reduces speckle in reconstructions of digital holograms. This is achieved by convolving the three dimensional intensity pattern (the intensity of the propagated DH at a series of different distances) with a 3D point spread function in all three dimensions (x,y,z). It is based on the fact that the addition of different independent speckle images on an intensity basis reduces the speckle content. We provide quantitative results in terms of speckle index and resolution, and show that filtering in the z direction has the added benefit of an increase in the depth of focus of the digital hologram reconstruction. (C) 2013 Elsevier B.V. All rights reserved.