Improved visibility of microcalcifications (MCs) and masses in tomographic breast imaging is a major concern in the medical imaging community, with intense research activity considering both hardware and processing approaches to the problem. Much of the research involves digital breast tomosynthesis (DBT). In this paper, we present results of human-observer studies that investigated the effects of postreconstruction filter strength on MC detection in DBT images generated at various dose levels. The use of human observers poses severe limitations on objective-assessment studies involving multiple parameters and this paper also discusses our continued development of a visual-search mathematical model observer as a substitute for humans. In this work, DBT images were created using a rigorous computer simulation applied to realistic breast phantoms. Acquisitions with 0.7, 1.0 and 1.5 mGy doses were modeled and the Feldkamp FBP algorithm was used for reconstructions. A set of 3D Butterworth filters with cutoffs representing moderate (0.2 cycles/pixel, with pixel size = 100 microns) to no (0.5 cycles/pixel) postfiltering were tested. LROC studies were conducted with four observers. As expected, MC detectability fell off with reduced dose. At the same time, the best MC detection for a given dose was obtained with unfiltered images, suggesting that the increased noise levels associated with lower dose cannot be overcome with postfiltering. The model observer showed promising results in terms of agreement with the human observers. The causes for some points of disagreement merit examination.