The present invention relates generally to polyimide composites having dispersed in the polyimide base matrix, useful spinel crystal fillers wherein the composite has a visible-to-infrared light extinction coefficient between and including 0.05 and 0.60 microns−1. The composite polyimides formed therefrom are typically used to make circuits having fine electrically conductive pathways adjacent to the polyimide substrate. These fine electrically conductive pathways are typically formed on the substrate using an electro-less metal plating step. First, the surface of the polyimide composite is light activated, typically by using a laser beam, then the light activated portions are plated to form thin lines, or pathways, on the film's surface.