Phase retrieval performed by the iterative Fourier-transform algorithm has been demonstrated through computer simulations for complex-valued objects with a known region of support. An active imaging system could artificially create an object with a known compact support by coherently illuminating a finite region of an extended object or scene. This points to the potential for novel coherent-imaging systems that form fine-resolution imagery utilizing far-field Fourier intensity measurements in conjunction with a priori knowledge of the illumination pattern. In this paper we describe the effects on phase retrieval of some of the measurement realities that would be encountered in an actual system. For example, any real illumination pattern will have tapered edges due to diffraction, and the effect of varying amounts of taper on algorithm convergence and quality of reconstruction are pre-sented. A modification to the algorithm, using an expanding support constraint, was developed to avoid stagnation problems associated with tapered illumination. In addition, the effects of a variety of errors in the data, both random and systematic, are presented. These errors include additive noise, quantization errors, and detector saturation and biasing.