IDKit internally converts all images to 500DPI before extracting template. For this reason, 500DPI images provide highest accuracy. Lower DPI images are accepted and they still provide acceptable error rates. DPI higher than 500 is unnecessary. IDKit DPI setting should be left on 500 if image DPI only slightly differs from 500 (for example, the 508DPI Upek scanners). This is because the conversion from 508DPI to 500DPI causes more loss of accuracy than slightly incorrect DPI setting.