A substrate including phosphor is remotely illuminated by an LED. Optical radiation that emerges through the substrate is measured. Portions of the substrate, such as raised features on the substrate, are then selectively removed responsive to the measuring, so as to obtain a desired optical radiation. In removing portions of the substrate, holes may be drilled through the substrate to provide a separate path for light from the LED that does not pass through the phosphor. Alternatively, a separate LED may be provided outside the dome.