Color separation systems and methods improve color constancy and smoothness of a color lookup table (LUT) for a printer. A plurality of nodes of the LUT may be defined in colorimetric space, and the nodes out of the printer gamut may be mapped to the printer gamut surface. A set of possible colorant combinations are then determined that produce each node in the LUT in a device independent color space using a non-linear minimization algorithm, such as, for example, a conjugate gradient algorithm. Next, a colorant combination may be determined for each and every node in the LUT based on an image quality metric. In some implementations, a smoothing filter may be used to smooth the lookup table.