How Does a Teleprompter Work? Technical Guide 2025
Teleprompters work by displaying scrolling text on a screen that's positioned in the speaker's line of sight. Professional systems use beam-splitter glass to reflect text while allowing the camera to record through it, creating the illusion of direct eye contact with viewers.
⚙️ Core Components
1. Display Screen/Monitor
The foundation of any teleprompter system. This can be a tablet, laptop screen, or dedicated monitor that displays the script text.
- • Brightness: 300-1000 nits for visibility
- • Resolution: HD or higher for clarity
- • Size: 10-20 inches typical
2. Beam-Splitter Glass
Special glass that reflects light at a 45-degree angle while remaining transparent to the camera.
- • 70/30 or 60/40 reflection/transmission ratio
- • Anti-reflective coating on camera side
- • Optical quality for no distortion
3. Scrolling Software
Controls text display, speed, formatting, and other presentation aspects.
- • Variable speed control
- • Font size adjustment
- • Mirror mode for reflection
- • Remote control capability
4. Mounting Hardware
Frames, rigs, and stands that hold everything in proper alignment.
- • Camera rail mounting system
- • Adjustable hood/shroud
- • Counterweight system
🔬 The Science Behind It
Beam-Splitter Physics
The beam-splitter glass works on the principle of partial reflection and transmission:
- 1. Light from the monitor hits the glass at 45°
- 2. ~70% reflects toward the speaker
- 3. ~30% passes through (lost)
- 4. Camera shoots through the glass
- 5. Speaker sees text, camera sees speaker
Light Path - Text
Monitor → Glass (45°) → Speaker's eyes
Light Path - Camera
Speaker → Through glass → Camera lens
📱 Software Teleprompters
Modern web and app-based teleprompters work differently:
How Our Web Teleprompter Works
- 1.Text Input: You paste or type your script into the browser
- 2.Processing: JavaScript formats the text for optimal readability
- 3.Display: Text appears in large, customizable fonts
- 4.Scrolling: Smooth animation using requestAnimationFrame
- 5.Control: Keyboard, mouse, or touch controls adjust speed
🎬 Professional Setup Process
Mount the Hardware
Attach teleprompter rig to camera rails, ensuring balance and stability
Position the Glass
Set beam-splitter at exactly 45° angle to both camera and monitor
Install Monitor
Place monitor flat below glass, facing upward for reflection
Adjust Camera
Position lens to shoot through center of glass without vignetting
Configure Software
Set mirror mode, adjust font size, and calibrate scroll speed
Test & Refine
Practice reading, adjust positioning, and fine-tune brightness
🎯 Scrolling Speed Mathematics
Optimal Reading Speed Calculation
Average speaking rate: 150-160 words per minute
Average word length: 5 characters + 1 space
Characters per minute: 150 × 6 = 900 characters
Lines per minute (60 char/line): 900 ÷ 60 = 15 lines
Optimal scroll speed: 15 lines per minute or 1 line every 4 seconds
🔧 Technical Specifications
| Component | Professional | Prosumer | DIY/Software |
|---|---|---|---|
| Display | 19-24" High-bright | 15-17" LCD | Tablet/Phone |
| Glass Type | 70/30 Beamsplitter | 60/40 Beamsplitter | None/Direct view |
| Control | Foot pedal/Remote | Bluetooth remote | Touch/Keyboard |
| Price Range | $2,000-10,000+ | $500-2,000 | Free-$100 |
💡 Common Issues & Solutions
Problem: Text appears reversed
Cause: Software not in mirror/flip mode
Solution: Enable horizontal flip in settings
Problem: Glass reflection visible in camera
Cause: Improper lighting or angle
Solution: Adjust glass angle, add hood, control ambient light
Problem: Text scrolls too fast/slow
Cause: Speed not matched to speaking pace
Solution: Practice and adjust to personal reading speed
Problem: Eye movement visible
Cause: Reading word-by-word instead of phrases
Solution: Practice reading ahead, increase font size
🚀 Try It Yourself
Experience How It Works
The best way to understand teleprompter technology is to try it yourself. Our free web-based teleprompter uses the same principles as professional systems.
Launch Free Teleprompter