Diffraction Enhanced Imaging (DEI) is a powerful X-ray imaging technique that allows the visualization of structures having different refraction and/or absorption properties with respect to the background. In DEI, the sample is irradiated with a monochromatic and highly collimated X-ray beam, and the outgoing beam is analyzed by means of a perfect crystal. A comparison was drawn among DEI images of a standard (ACR) and a custom phantom using different harmonic diffraction orders. Images were obtained at two different synchrotron beamlines, the SYRMEP beamline at Elettra and the X15A beamline at the NSLS (Brookhaven, NY), utilizing a double-crystal Si monochromator and a single-crystal Si analyzer, operated in the symmetric, non-dispersive Bragg configuration. The harmonic order was separated by placing a refractive prism between the two crystals of the monochromator. The use of the and the reflections resulted in a 5-fold improvement in the analyzer angular sensitivity, consequently enhancing the extinction and refraction contrasts with respect to the reflection. The detail visibility was improved by 1-2 orders of magnitude. By means of the refractive prism technique, even higher harmonics might be used, thus promising even better image quality.