Bildprompt
Vertical abstract optical study with canvas ratio 848:1264, approximately 2:3. A single very soft horizontal oblong band of colored light floats across a nearly uniform warm charcoal gray field. Keep the upper 42 percent and bottom 28 percent mostly empty and dark. The luminous form spans essentially the whole canvas width, running from a cropped diffuse left edge to a rounded right end near x98%, centered around y57%. Its brightest body sits between y46% and67%, with a wide fuzzy halo fading out by y72%. The upper and lower contours are almost horizontal, subtly curved, with no sharp border or physical object edge. Do not draw a outlined capsule or an interface button.
The left third grades from saturated violet along the far left through electric blue into cyan. The large middle is pale turquoise cyan. The right central area is soft pale icy blue, nearly whitish but not pure clipped white. A narrow luminous yellow arc curls around the rounded right end, surrounded by orange and a blurred red outer halo. Along the lower boundary, violet and magenta appear at the left and middle, turning orange red under the right half. A thin orange red upper fringe starts around the middle and follows the top toward the right. These colors merge continuously with broad optical softness; no separated rainbow stripes or hard vector contours.
The glow sits slightly below the canvas center, leaving much greater dark headroom than the light band's own height. Background remains charcoal with subtle brown and muted green undertones, no horizon, room, shadow, cast reflection or visible projector. Apply fine analog photographic grain uniformly across the dark background and soft color fields. Keep the impression of a heavily defocused prismatic light experiment, luminous but restrained. There are no text, letters, symbols or representational objects. Negative constraints: crisp geometry, glass prism object, lens flare star, multiple bands, vertical rainbow, saturated background, hard gradients, outlined pill, UI mockup, smooth sterile vector art, white canvas, border, watermark or typography.