If you’re not familiar, a ring light is simply a bunch of light sources arranged in a circle, with a hole in the middle, and the hole lines up with a camera’s lens. Usually it screws right in to the front of the lens, and then a cable plugs into the camera where the xenon flash lamp would normally go, in order to get the flash trigger signal from the camera.
The light is either always on, or only on when the flash signal is triggered.
Ring lights are about $60 each for a basic Chinese import model.
Now I’ve been thinking, the circuit should be pretty simple - it should be possible to make your own.
What I’m not so sure about is the 3D printing aspect. The ring-shaped PCB must be affixed to the lens, and the flash hotshoe needs a plastic shape with metal contacts to actually get the flash signal. There also needs to be a way to get power to the LEDs - perhaps a battery holder somewhere.
One idea I had was to get an extension tube, step-up ring, or filter holder, and just glue it to the PCB, or to the plastic holding the PCB. That would provide the necessary threading to actually screw onto the lens.
You can use an old flash unit as battery holder/trigger signal generator. Just remove the actual flash and the high voltage circuit. You can then connect it to the ring unit with a cable. As for mounting the ring onto the lens you could use filter ring adapters that you could screw onto the front lens and then mount the pcb onto it with screws.
In my experience ring flashes are almost always used with additional fill and back flash units. The setups let you control timing, duration and intensity of each light source. By building your own you would need to either build the sophistication into your design or limit yourself to flat looking pictures due to the lack of controlled shadows.
I don’t know what kind of purpose you have for the ring flash, so it may be a benefit or drawback. If you are thinking of portraits, i would like to suggest a studio photography class at one of the community centres or night school at the school board. It will give you a glimpse of the lighting complexity involved in studio photography.
I’m pretty sure LED’s can turn on/off far faster than the 1/125s or 1/250s shutter speed used for flash photography.
There is an effect called shutter curtain where the flash goes off while the shutters are still opening or closing, which results in a portion of the image having the wrong exposure. Prosumer and above cameras disclose their shutter opening/closing times, so all you need to do is delay the flash sufficiently.
