- Digital Image Correlation (DIC) is an optical, non-contact method to measure full-field displacements and strains. The only requirement is that the test specimen has a random speckle pattern on its surface, either generated by the experimentalist (i.e. random paint pattern) or occurring naturally (i.e. surface texture at large magnifications). There is no inherent length scale to DIC - by choosing the appropriate magnification of images and the corresponding speckle size, DIC can be used to measure displacements from the meter scale to the micron scale.