The overlap where two projectors share one picture

A bar, split into four. Two small circles above it, near either end. Below, two long rectangles that almost meet — except for one short stretch where they overlap.

Nothing on it is labelled, and everything on it is a schedule.

What does the diagram actually show?

Two machines handing a picture to each other without a visible join.

One projector is running a reel; a second projector, already loaded and warmed up, is standing by. For a short stretch near the end of the first reel, both machines run at once — the second one picking up the picture while the first one is still projecting it — and then the first shuts down. The bar is the timeline of that handover. The overlap is the only part of the whole schedule where two machines are doing the job simultaneously.

Everywhere else on the bar, exactly one projector is running. The overlap is deliberately the smallest part of it.

Why two circles rather than one?

Because the handover needs two separate instructions, seconds apart, done by the same person.

The first circle marks the point where a projectionist starts the second machine. The second marks the point where the first machine is closed down and the picture on screen has fully passed to the new reel. One cue without the other leaves either two pictures overlapping on the screen, or a gap with no picture on it at all. The mark that carries each of those cues is tiny and easy to miss on purpose — the diagram here is the two-part instruction it triggers, drawn at the scale the job actually happens at.

Why is there nothing written on the bar?

Because the sequence is the information, not any specific number.

Four seconds, two projectors and two cues describe the shape of the job in any booth running any reel — put a number on the bar and it stops being a general description and starts being a claim about one particular room's equipment. Leaving it unlabelled is what lets the same diagram describe the job everywhere it's still done.

Can I use a diagram like this freely?

Yes — a timing diagram of a standard procedure isn't authored artwork, it's closer to a wiring schematic. Nobody owns the shape of two overlapping rectangles on a bar.

What would need permission is a diagram redrawn from a specific manufacturer's manual, with that manufacturer's own labelling and house style reproduced exactly. A generic bar with no branding and no numbers on it, like this one, isn't tracing anybody's proprietary drawing.

Is this a print for one person or two?

It reads well as a pair — one projectionist in the first rectangle's ink, a colleague or a partner in the second, both wearing the same bar.

It's one of the few diagrams here where the shirt still makes sense worn alone: the whole point of the overlap is that, for four seconds, two people are doing one job together, and a single wearer can stand for either half of that. It sits alongside a card of cues for the room's lighting as the same kind of instruction, aimed at the same booth, for a different part of the show.

Isn't four seconds too short to matter?

That's exactly the size of the job, and the diagram is built to make a short window look like the event it actually is.

Four seconds is long enough for two irreversible actions and short enough that almost nobody in the seats notices it happening. The audience's experience of a continuous film across the whole running time rests entirely on that short overlap going right, every time — which is a larger claim than the window's length suggests, not a smaller one. The running order the projector is serving comes from a sheet decided in advance, but the changeover itself happens in real time, with nothing to fall back on if it's late.

Does it print well?

Very well — it's a diagram built from flat rectangles and hard ticks, which is exactly what survives printing best.

Keep the bar's segments crisp rather than shaded, the two circles small and solid, and the overlap in one contrasting ink against the two rectangles' base colour. Fine gradients would blur the one detail that matters — where the overlap actually starts and ends — so there shouldn't be any.

Slate, ink blue or charcoal grounds suit it. Two inks: one for the bar and rectangles, one for the overlap and the two circles.

How do I get one made?

Describe the handover at JustOG — how long the overlap reads, where the two cue points sit, which projector's ink goes where. Pick a direction, drag the crop frame, see it composited on the real garment, and it's made to order and shipped.

Designs other people have published are in the shop.

For four seconds, two machines are running the same film, and then only one of them is.