1. A process comprising: using a processor for: capturing a reference image; capturing a current image; calculating reference image to current image object plus shadow ratios (RTOPS); calculating reference image to current image object ratios (RTO); calculating reference image to current image shadow ratios (RTS); calculating an average RTOPS ratio; calculating an average RTO ratio; calculating an average RTS ratio; calculating a first range using said RTOPS, RTO, and RTS ratios; identifying a pixel as being under a shadow by multiplying a lower limit of said first range by said average RTOPS ratio and multiplying an upper limit of said first range by said average RTOPS ratio, thereby giving a second range; and determining whether said pixel falls within said second range.