How a teleprompter works — the principle behind every build
A half-silvered mirror — also called beam-splitter glass — transmits approximately 70% of light and reflects approximately 30%. When mounted at 45 degrees in front of a camera lens, it reflects the image of a display positioned beneath it directly into the line of sight of anyone standing behind the camera. The camera, looking through the glass from behind, does not capture the reflection — only the scene beyond.
The result: the presenter sees the script text floating in mid-air, centered on the camera lens. The camera sees the presenter apparently looking directly into the lens. The script is invisible to the camera.
For a DIY build, you need three things: 1. A beam-splitter surface at 45 degrees in front of the lens 2. A display positioned beneath that surface, facing upward 3. A frame that holds both in the correct position
Everything else — build material, frame design, mounting method — is an implementation detail.
Build 1: The 20-minute cardboard prototype ($5–10)
Materials: — One sheet of beam-splitter window film (available on Amazon for $8–12 per sheet; one sheet builds multiple rigs) — Cardboard or foam board (cereal box quality or heavier) — Tape and scissors — A phone or tablet as the display
Build:
Step 1 — cut the frame. Cut two rectangles of cardboard equal to the width and height of your phone. Cut two identical triangles with a 45-degree angle. These form the sides of the frame.
Step 2 — assemble the box. Assemble the cardboard into an open-topped box — four sides, no top, no bottom — with the two triangular sides holding the internal angle at 45 degrees.
Step 3 — attach the beam-splitter film. Cut the beam-splitter film to match the diagonal opening of the box. Tape it across the 45-degree opening, pulling it taut to avoid wrinkles. The film is your mirror.
Step 4 — place the display. Place your phone face-up on the bottom of the box, beneath the film, displaying the script in SyncedCue. The camera sits at the open front of the box, behind the film.
Step 5 — test the reflection. Look through the film from the camera position. The phone display should be visible as a reflection, appearing to float in front of the lens. Adjust the film angle until the text appears centered.
Limitations: Cardboard builds are not durable or weather-resistant. They work for testing, learning, and low-stakes recording. Upgrade to foam board or PVC for a more permanent build.
Build 2: The foam board rig ($15–20)
Materials: — Beam-splitter film (same as Build 1) — Foam board (available at craft stores, $3–5 per large sheet) — Strong tape or hot glue — A phone or tablet as the display
Build: The construction process is identical to Build 1 with one change: replace cardboard with foam board throughout. Foam board is stiffer, holds angles more precisely, and does not degrade with handling the way cardboard does.
Cut the panels to match your display device, assemble with hot glue at the joints, and attach the beam-splitter film across the 45-degree face. The result is a rig that holds its calibration between sessions and handles moderate use.
Improvement over Build 1: Foam board holds the 45-degree angle more consistently than cardboard. The reflection alignment is more stable, which reduces the need to re-adjust between takes.
Build 3: The PVC pipe rig with glass panel ($25–35)
Materials: — Half-silvered glass panel (10x10 inches, available from teleprompter glass suppliers for $15–25) — PVC pipe and fittings (1/2 inch diameter; hardware store, ~$8) — PVC cement or strong tape — Camera mount adapter
Build:
PVC pipe forms a rectangular frame that mounts in front of the camera lens. The frame holds the glass panel at 45 degrees. The phone or tablet sits in a holder beneath the glass, facing upward.
Frame dimensions: The frame opening should be slightly larger than your camera lens diameter. A 5x5 inch opening works for most DSLR and mirrorless lenses up to 77mm diameter.
Glass mounting: The glass panel slots into a channel cut into the top and bottom PVC pieces, or is secured with adhesive at the edges. It must sit at exactly 45 degrees — verify with an angle app.
Display holder: A phone holder or tablet stand positioned beneath the glass frame holds the display facing up. Adjustable phone holders allow repositioning for different device sizes.
Advantages over film builds: Proper glass does not wrinkle, does not degrade over time, and produces better contrast in mixed lighting conditions. The PVC frame is rigid and replicates the calibration between sessions without adjustment.
The software side: completing the DIY setup
A DIY rig with a fixed-scroll app produces the same robotic delivery as a commercial rig with a fixed-scroll app. A DIY rig with voice scroll produces the same natural delivery as a commercial rig with voice scroll. The glass and frame do not determine delivery quality — the scroll method does.
SyncedCue runs in any browser on the phone or tablet you are using as the display. Open the script, enable voice scroll, and the setup is complete. The text scrolls as you speak, stops when you pause, and tracks your natural delivery pace automatically.
Display settings for DIY rigs: — Mirror the display horizontally in SyncedCue so the text reads correctly when reflected in the glass — Set font size to 40–60pt to allow reading without eye movement at your filming distance — Enable dark mode for better contrast in the reflected image
Important: SyncedCue's horizontal mirror mode is specifically designed for teleprompter use — the text is flipped so it reads correctly in the beam-splitter reflection.