How to mirror teleprompter text for a beam-splitter rig

Why the text has to be reversed

A beam splitter is a piece of half-silvered glass mounted at 45 degrees directly in front of the lens. Your display sits below or above it, facing the glass. The glass reflects the script back at you and lets the camera see straight through, so you read and look down the lens at the same time.

A reflection reverses whatever it shows. Send unmirrored text to the rig and you read it backwards, so the script is flipped in software first: two reversals cancel out and the reflection reads normally.

Which axis to flip

• Horizontal for a conventional rig where the display sits below the glass. This is the common case.
• Vertical for an overhead setup where the display is above the glass and the image also arrives upside down.
• Use neither if you are reading the screen directly with no glass in the path, because mirroring would only make the text unreadable.

If you are unsure, hold a phone up to the glass before mounting anything. Whichever way the text reads backwards is the axis you need to flip.

Sending the scroll to the rig

The rig's display should show the script and nothing else, while you keep speed, pause and font controls on your own screen. On macOS that means a duplicate prompter window sent to the external display, mirrored, with the control window staying put.

1. Connect the rig's display and set it as an extended display, not a mirrored one.
2. Open a duplicate prompter window and move it to that display.
3. Turn on mirroring for the duplicate window, on the axis you established above.
4. Full-screen the duplicate so no menu bar or window chrome reflects into the glass.
5. Check the reflection, not the screen. The reflection is what you will actually be reading.

For more on setting up the rest of the shoot, see the full Mac teleprompter guide.