Bubbles

Soap bubbles drift through the frame and bend the light passing through them. Each one is a small lens carrying a distorted copy of the room.

They read as childhood, as fragility, and as a moment that is about to end. The audience knows every one of them is going to pop.

Ask for refraction, as the note says. A bubble is a thin transparent shell, so it inverts and compresses whatever is behind it, and it is that inversion that stops it rendering as a grey ball.

The film on the surface splits light into colour bands that shift as the bubble turns. Those moving bands of magenta, green and gold are the most recognisable thing about a bubble.

The motion is a rise with a wobble. They go up slowly, drift sideways on the air, and turn as they go. A bubble moving in a straight line at a constant speed looks like a sphere on a path.

Use it for childhood, for a party, for a bath, and for any beat that should feel temporary.

Skip it when the frame is busy. Bubbles are transparent, so a detailed background swallows them completely.

Particles are opaque specks that catch light on their surface. Bubbles are transparent shells that light passes through, which is why they carry a picture of the room and particles do not.

The test is whether you can see through them. Points of light are particles. Spheres with the background showing through, upside down, are bubbles.

Opaque grey or white spheres come back. Say they are translucent and refracting, with the background visible and inverted through each one.

The second failure is still air. Ask for a slow rise with a sideways drift and a turn, so they behave like something being carried.