Lumens is a measure of the total available light. Emitter lumens is pretty well fixed for a given voltage input or regulation. Out the front lumens could be effected by the quality of the reflector, less loss of light thru absorption vs reflection. Larger as well as deeper reflectors can control the available lumens better and increase the intensity of the hotspot, less spill. This intensity is measured in lux or candella and directly relates to the throw of the beam.