In most optic systems images are captured using a CCD/CMOS sensor, where the phases of the converted photons are inevitably lost. Fourier Ptychographic Microscopy (FPM) circumvents this issue by capturing normal microscopy images, and Fourier transforming them computationally (hence the name). Reconstructing the complex object not only yields amplitude but also phase information, enhanced up to super-resolution. Yet one disadvantage remains unsolved: FPM is a very ill-posed problem, the algorithm is not guaranteed to converge to the correct solution, if it converges at all. In practice this means that there is reasonable doubt if the recovered image actually represents the object under the microscope. This work inquires the quality of FPM reconstruction under variation of important system parameters in simulation and experiment. It shows that the alignment of the illumination source is quite critical: even 0.2 degrees off renders reconstruction useless. This paper thus furthers the costbenefit analysis of which amount of computation time should be spent on digital post-correction.