I used it on car headlights a loooooooong time ago for a contest here. ( Asian girl in a tunnel ) ("Kicked to the curb" or something like that) and it did a good job of looking like what headlights should look like. Probably could have done it a different way but it worked so I went with it. I used it on the cell phone camera light and after trying three different patterns I think I went back to the second one. It kept the light where I wanted it. However, it didn't work well with the screen so the screen is just illuminated normally.
Id say if you are looking for a specific look like certain lamps that just face up/down then its worth a try. If you find a few favorite patterns its probably faster to save a few light resources with them applied. I haven't really tested them thoroughly since you can get about 90k or more online free.
Best thing is to try a handful and see if you think its worth it. I think in some cases yes and some not so much.
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