When a print is coated with a transparent layer. such as a lamination film or a varnish layer. its color can be modified compared to the uncoated version due to multiple reflections between the layer-air interface and the inked substrate. These interreflections involve a multiple-convolution process between the halftone pattern and a ring-shaped luminous halo. https://www.roneverhart.com/AMS-Neve-1073SPX-Single-Preamp-and-EQ-p33827/