This is a flash ring for my Canon EOS 60D.
I did it for a 67mm diameter optic.

I have some pieces of 12v LED strips and i used to make this flash ring.
The inside of the ring is covered with aluminium foil (to make it more reflective).
The external cover is made with some gaussian plexiglass (or you can print a thin layer or white PLA).

To let the 12v LED power on, i tought of some solutions:

• make a battery pack of 8 AA battery (1.5v*8=12v)
• use a powerbank (output 5v) with a potenziometer to trasfor it in 12v
• use a 9v battery with a potenziometer to trasfor it in 12v

I chose the last one, 9v battery + potenziometer, couse the size is smaller and the weight lower. So i have printed a box that goes to the camera flash slider for having them inside.
And works perfectly!

UPDATE: for who's interested, i added the flash slider box .stl here: https://www.thingiverse.com/thing:3956521