There is an annoy trend in bike tail light. The vendors are making super bright LED tail light. The idea is the brighter the light, the easier it is for drivers to see, and the safer it is for the riders. But there is diminishing return to the brightness. It is no more safe when the light is bright enough to see one mile away, v.s. a moderately bright light that you can see from half a mile away. Instead, a very bright tail light causes big problem to the rider behind you. It is blindingly bright to follow other with these super bright light.
I have a new light that's somewhat bright. I decided to make some modification to similar frosted glass to make the light more defused and more comfortable to others. Here is the result
Simply scratch the plastic surface with a file or rough rocks. Don't be gentle. This is how my light looks like after I scratched it.
From a distance, there seems little difference between the two lights.
I hope we stop buying these super bright tail lights. If you have one, consider scratching it to make it more comfortable to look at.