I was inspired by the rainbow portrait trend to create a tool for precisely positioning a prism. This 3D printed prism holder cradles the glass while providing freedom to rotate for that perfect angle. The holder can be mounted on a c-stand or tripod, and comes together quickly with the attached STL files and a couple of nuts and bolts from the hardware store. Although I created it as a photography tool, it could also be used for physics demonstrations.

Supplies

Prism
3D printer (I used a Creality CR10S Pro)
3D printer filament (I used Hatchbox silver PLA)
2x 10-24 bolts (1/2" long)
2x 10-24 nuts
Baby pin with female 1/4-20 (also available from Adorama) along with a 1/4-20 screw and washer (for C-stand mounting) or light stand adapter
or make the mounting hole a little bigger and install a threaded insert for attaching a tripod plate

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Step 1: 3D Design & Printing

I designed the prism holder in Tinkercad, which is free and easy to use. You can copy my design and alter it to fit the exact dimensions of your prism, or to make improvements.

If you'd prefer to print the holder as-is, you can find the STL files attached to this step, on Thingiverse, and you can also export them from Tinkercad too.

I printed out one of the long spanner piece and two each of the round pieces.

Print settings:

Rafts:No
Supports:No
Resolution:.2mm
Infill:20%

Disclosure: at the time of this writing, I'm an employee of Autodesk, which makes Tinkercad.

Step 2: Assembly

Press a hex nut into the hexagonal cutout of the end caps.

Insert a screw into the round piece with the triangular cutout, then from the inside of the spanner through the hole. Add the end cap, such that the hex nut is on the outside of the sandwich, and the threads catch. Tighten until the knobs are snug but can still be hand-adjusted.

Test fit your prism, one end at a time. My prism is 200mm long. If yours does not fit lengthwise, adjust the spanner piece in Tinkercad and print a new one to fit your prism's dimensions.

Step 3: Mounting Options

If your prism fits, temporarily remove it in order to add the mounting hardware. I chose to use a 1/4-20 bolt, a washer, and "baby pin" which is compatible with C-stands, which are ever-present on set. This way, the prism can be positioned precisely anywhere in a scene. You could choose to use a light stand adapter if that works better for you, or even made the hole a little bigger and use a 1/4-20 threaded insert to make it tripod-compatible. Mounting options abound! Tell me about yours in the comments, please!

Step 4: Use It!

Once you mount your prism holder on a stand, position it in direct sunlight between the sun and your subject. If your shooting environment's direct sunlight isn't optimal, you can use a mirror to bounce it. For instance, the photo/video shoot for this project involved taping a 12" square mirror to a baby pin mount, and putting it on a tiny stand out on the roof deck. This enabled us to angle the mirror any way we needed to bounce the light more directly into the room, so we ultimately gained control over where the rainbows land in the room.

Thanks for following along! If you make your own prism holder, I'd love to see it and your photography in the I Made It section below!

If you like this project, you may be interested in some of my others:

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