The Creative Flash Photography book actually recommended stripping an old film camera to use as gobo projector. I didn’t have one I’d like to strip. Instead my husband 3D printed one for me. Works just as well. It attaches the lens to a speedlight. In this case a Yongnuo 568 EX II.
I also attached it to a studio strobe snoot. And it takes away a lot of power – that’s for sure. Out of the 500Ws that I have on my oldest Elinchrom, I didn’t get enough light to even balance my speedlight to more than 1/64 power (and the speed-light was inside a soft box)
The principle is that you make a gobo-template, or if you already have one. You project the light through the template and through a lens and try to focus the light on the background. It’s really cool, but a bit tricky to make work. Focusing and zooming needs to be done from the hip.
The 3D-models for the gobo-projector adapter can be found here: