DavidEF
(DavidEF)
32
It’s not that it needs to be phone powered. It’s that holding a phone up for use as a camera can often take both hands. It’s a convenience to have this thing hanging off the end of the phone, so it gets pointed the same direction as the camera at all times. To that end, being powered by the phone is a convenience as well.
As for the efficacy of the light, well, it depends what you’re doing with it. It seems to me this light isn’t something you’ll need. 