In this study two-dimensional mixed mode stress intensity factors for a crack tip in the neighborhood of a free edge or another crack tip were determined both experimentally and numerically;In the experimental approach on-line digital image analysis procedures are used to extract photoelastic data from the whole field isochromatic fringe patterns. Two different techniques were used to obtain information on the near crack tip stress field: (1) Half Fringe Photoelasticity (HFP), which requires adjusting the load to keep the maximum fringe order less than 0.5 in the data extraction zone, and (2) Trace, a digital fringe sharpening procedure, which accurately produces trace of all half- and full-order fringes. The load is adjusted to yield multiple fringes in the field of data extraction;Numerical SIFs were determined by the boundary integral equation method and compared to experimental results.