Speckle fields are ubiquitous in nature: the familiar examples are the light transmitted through scattering biological tissues and the acoustic wave scattered from complex obstacles. Although highly
randomized, speckle fields contain the essential information regarding the complex structures that interacts with a coherent wave. Here, we propose a simple method to retrieve the phase and
amplitude of speckle fields without complicated instruments. Exploiting the self-interference of speckles, complex field information can be computationally reconstructed with a simple perturbation
on the intensity-measurement system. We expect that the proposed method will be widely adapted in various fields, from biophotonics to industrial holographic measurement, thanks to the simplicity.