As set forth herein, a computer implemented method is used to detect synchronized defects in documents. Profiles of single separation test targets are characterized for one or more toner colors. A spatially varying toner reproduction curve (TRC) is constructed for each profile on terms of an area coverage in versus area coverage out. A profile is extrapolated for each color of interest and a CMYK profile is applied to obtain a correlating L*a*b* profile for each color of interest.