Most flashlights with an aspheric lens seem to have various rings. Is this a necessity with an aspheric or something that can be avoided with a better quality aspheric?
I'm not taking about the "Cree Ring" or the artifacts present when using as aspheric with a reflector.
Just using an aspheric alone you frequently see the bright emitter area, then the Cree Ring (which can be painted out) and then a dark area and then another ring of light, another dark area and then another ring of light.
I've done a little testing and this seems to come from the aspheric itself and not from the emitter or reflections inside the head, or from anything external to the aspheric.
Is this just because it's a simple (as opposed to complex multi-lens system) lens? What is actually causing those rings?