Build guide
DIY teleprompter glass, explained.
The frame is a hobby project. The glass is the part that either works properly or does not, and it is the part most guides gloss over.
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Quick answer
DIY teleprompter builds need beam splitter glass with a coating, not plain window glass, which causes double-reflection ghosting. The industry standard is a 70/30 or 60/40 transmission-to-reflection coating on thin glass around 2mm thick, mounted at a 45-degree angle. Beam splitter glass is sold pre-cut in common sizes by teleprompter accessory sellers and on Amazon.
Why you cannot just use a picture frame's glass
This is the mistake almost everyone makes on their first attempt, because it seems obvious: glass is glass. It is not. Plain window or picture-frame glass has no coating, so it reflects a little light off the front surface and a little more off the back surface, at slightly different angles. The result is a faint double image, called ghosting, sitting behind your actual reflection. It is subtle enough that you might not notice it staring at the glass, and completely obvious the moment you watch back footage shot through it.
Real teleprompter glass, called beam splitter glass, has a thin coating applied to one side specifically to control how much light reflects versus passes through, in a single clean layer rather than two competing ones. That coating is the entire product. Everything else is just a sheet of glass.
The ratio you'll see everywhere: 70/30
Beam splitter glass is sold by its transmission-to-reflection ratio. 70/30 means 70% of the light passes through the glass to the camera, and 30% reflects your screen back at your eyes. You will also see 60/40, which reflects a slightly brighter image at a small cost to how much light reaches the camera, and occasionally the ratio written the other way round as 30R/70T. It's the same measurement, just ordered differently, so check which number has the R and which has the T rather than assuming.
70/30 is the industry default and the right choice for most setups: bright enough to read the reflection comfortably while leaving the camera plenty of light to work with. 60/40 is worth considering only if you are shooting in a dim room and struggling to read the screen, since the trade-off is a slightly darker image for the camera.
Sizing it to your screen
The glass needs to be at least as large as the screen it's reflecting, measured diagonally, because it sits at an angle and you're viewing it from further back than the screen itself. Common pre-cut sizes track common device sizes for this reason: a 12-inch sheet for a phone or small tablet, 14 to 17 inches for a full-size tablet or a small monitor. If your screen falls between sizes, size up rather than down. A slightly oversized sheet just means a bit more frame around the edge; an undersized one crops your own text.
Thickness matters more than people expect. Most teleprompter-grade sheets run close to 2mm, thin enough to keep the reflection sharp. Thicker glass — anything closer to what you'd use for a tabletop or a picture frame — introduces its own faint secondary reflection between the front and back surfaces, which is a milder version of the same ghosting problem plain glass has.
The 45-degree angle isn't optional
The glass sits between your camera and your subject at a 45-degree angle. At that specific angle, the screen below reflects straight up into your eyes while the camera behind the glass looks straight through it at whoever is being filmed. Steeper or shallower angles still sort of work but throw the reflection off-centre from where your eyes naturally rest, which quietly reintroduces the off-axis look a teleprompter is supposed to eliminate. Build the frame to hold the glass at 45 degrees deliberately, not by eye.
Where to actually buy it
- Pre-cut beam splitter sheets sized for common teleprompter frames are sold on Amazon by several sellers and by dedicated teleprompter accessory shops, generally for somewhere in the $15 to $40 range depending on size.
- Specialty optical suppliers will cut a sheet to a custom size if none of the standard dimensions fit your build, at a higher price.
- Don't substitute acrylic beam splitter film stuck to plain glass unless you have used that specific product before. Cheap film has a habit of introducing visible waviness that a proper coated sheet does not.
Handling and mounting
- The coating sits on one face only. Check with the supplier which side it's on and mount it facing the correct direction — the coated side generally needs to face your reflected screen.
- Clean it with a microfibre cloth, not paper towel, and avoid glass cleaners with ammonia, which can degrade some coatings over time.
- It's still glass. Corner guards or a foam-lined frame edge are worth the few extra minutes, since a chipped corner shows up as a distracting reflection right where your eye tends to land.
Once the glass is mounted, the text needs flipping
The reflection off any mirror or beam splitter flips the image horizontally, so whatever is on the screen underneath needs to be pre-flipped for it to read correctly once it bounces up at you. This is what mirror mode does in software, and it is the single most common thing people forget after finally getting the glass itself right — you'll assemble the whole rig, turn it on, and be reading backwards. More on mirror mode.
Frequently asked questions
Can I use regular glass for a DIY teleprompter?
No. Plain glass has no coating and reflects light off both surfaces slightly differently, producing a visible double image called ghosting. You need beam splitter glass, which has a coating applied specifically to control the reflection.
What does 70/30 mean on teleprompter glass?
It is the transmission-to-reflection ratio: 70% of light passes through to the camera, 30% reflects your screen back to your eyes. It is the industry standard ratio. 60/40 gives a brighter reflection at a small cost to how much light reaches the camera.
What size glass do I need?
At least as large as your screen measured diagonally, since it sits at an angle and is viewed from further back. 12 inches suits a phone or small tablet, 14 to 17 inches suits a full-size tablet. Size up rather than down if unsure.
Why does the angle have to be 45 degrees?
At 45 degrees the screen below reflects straight up to your eyes while the camera behind the glass looks straight through at you. Other angles still work loosely but shift the reflection off-centre from where your eyes naturally sit.
My text reads backwards through the glass. What did I do wrong?
Nothing wrong with the build — the reflection flips the image, so the display needs to show the text pre-flipped. Turn on mirror mode in your prompter software and it will read correctly.