Prism Effect
Prism effect for photos and video: colors split into rainbow fringes that smear away from the center or along one direction, with fisheye or pinched glass.
Why does a prism make rainbows?
Glass bends each wavelength of light by a slightly different amount, more for violet than for red. That's called dispersion, and a prism makes it obvious: white light goes in, and a fan of colors comes out. Photographers hold a prism or a crystal in front of the lens to throw those rainbow smears across a portrait.
This effect copies the result. It samples the picture several times along a short line, each sample tinted a different color of the spectrum, and blends them, so edges and highlights split into rainbow fringes.
The settings
Spread is how far the colors drift apart, and Steps how many rainbow samples make up the smear, from 3 up. Few steps show as separate colored copies, and many blend into a smooth band. Radial at 1, the default, smears away from the center like a lens, and at 0 it smears in one direction, set by Angle, like a prism held to one side.
Sharp centre keeps the middle of the frame clean and Sharp edges keeps the border clean. Lens bows the picture out like a fisheye above 0, or pinches it in below 0. Turbulence twists the smear through a noise field, which looks like old, uneven glass.
Which preset should you start from?
Prism is a radial smear across the whole frame. Rainbow edge keeps a portrait's face clean in the middle and fans the colors out toward the border, which is the classic prism-photo look. Slant is a one-way smear at 30 degrees.
Fisheye and Pinched add a lens shape, Uneven glass adds turbulence, and Grey smear turns Colour to 0, which leaves a plain directional blur. If you only want the thin red and blue edges of a cheap lens rather than a rainbow, the Glitch Effects hub has a chromatic aberration tool for that.
Combining it with light
The rainbow is strongest on bright edges, so a backlit subject or a picture with a sunset works better than a flat, evenly lit one. Bloom Effect after it makes the colored fringes glow.