Digital holographic microscopy is a quantitative phase measurement technique that can provide nanometer resolution of the thickness or surface profile of an object. We analyze the influence of additive noise in the hologram plane on the accuracy of phase measurement. We analyze Gaussian distributed and Poisson distributed shot noise in the camera plane and we develop a model for quantifying the phase error in the reconstructed phase. [Figure not available: see fulltext.] Â© 2011 3D Display Research Center and Springer-Verlag Berlin Heidelberg.