A beam-splitter rig is one idea and one piece of glass. The glass sits at forty-five degrees in front of the lens, coated so that it behaves as a mirror on your side and a window on the camera’s. Your screen lies flat in a tray below it, facing up; you see its reflection floating directly over the lens; the camera looks straight through the glass and sees only you, because a hood behind it keeps stray light off. The whole point is the axis. On a bare phone, the script sits centimetres below the front camera, and viewers can see your eyes riding that gap. In a rig, the words and the lens share one line of sight, so you read every word while looking exactly into the camera. Studio prompters have worked this way for seventy years, and a phone in the tray is a perfectly good screen for one.
The glass is a mirror on your side, and mirrors reverse what they show. Put ordinary text in the tray and you will see it backwards in the glass — so the source has to be flipped in advance. The prompter draws the script mirrored horizontally, the reflection reverses it again, and you read it the right way round. Some rigs want a vertical flip as well, or instead; it depends on which way the tray holds the phone and which edge faces the glass, and rigs genuinely differ. Do not reason it out from optics. Sit where you will present, look into the glass, and if the text reads wrongly, change the flip until it reads. Talk2Camera mirrors both ways — horizontal and vertical — for exactly this, and the setting changes only what the prompter draws. Your script stays the right way round everywhere else in the app.
A phone that lives in the tray should be a prompter and nothing else, which is what Rig Mode is: the script full screen, no camera preview, nothing recorded — the mode never even asks for camera access. This is practical rather than tidy-minded. A camera preview under the glass is wasted pixels and wasted battery, and an app that records is an app that quietly fills a phone’s storage across a long session for nothing. In the rig, the phone’s entire job is to be a bright, legible screen while the real camera — a mirrorless body, a cinema camera, a second phone — sits behind the glass and does the filming. Two settings matter more than any other: brightness up, because the glass costs you some light, and text large, because the reading distance is the presenting distance.
The last problem a rig creates is reach. The prompter phone is inside a hood, behind glass, at lens height — the one place on set you cannot casually tap. Touch it mid-take and you risk nudging the rig; a nudged rig means reframing, and the take is over anyway. So pair a remote before you need one. Talk2Camera takes a Bluetooth keyboard or a game controller: scroll, pause, change speed and start recording, from your hand, your lap, or a table off frame. Mid-take, that means rolling the script back to retry a line, or holding it while you improvise, with your hands never entering the shot and never touching the glass. A cheap controller in a jacket pocket covers all of it — and the rig becomes something you touch twice a day: once to build it, once to pack it away.