An improved two-load method for whole-field complete determination of photoelastic parameters is presented. The dark-field isoclinic images are used to determine the isoclinic angles. Using two isoclinic maps obtained from two different loads effectively compensates the indeterminable points. The use of dark-field and light-field photoelastic images for normalization extends the two-load method to analyze dark-field photoelastic fringe patterns and avoids model movement. Larger errors on the determined fringe orders are further reduced by a least-squares quadric fitting. The results are compared well to the theoretical ones. Further comparison of the improved two-load method and the two-wavelength method are given.
