[en] The effects of the angular range of data taking in reconstructions in planar positron cameras using the deconvolution method and the matrix method, respectively, are investigated. It is found that in the absence of any a priori information there are undetermined components in the reconstruction if the field of view of the positron camera is limited. However, most of the undetermined components are recovered in the case in which the transverse spacing of the object is discrete, and all of them are recovered if the fact that the object extent is finite is utilized. It is concluded that the two reconstruction methods are mathematically equivalent. The results obtained can be applied to other transmission and emission imaging devices