Mid-day mist rainbows need fast shutter; dusk needs a tripod.

For mid-day, start at ISO 100, f/8, 1/500s and adjust. For dusk, ISO 400, f/5.6, 1/30s on a tripod.

Mid-day light is harsh and the mist will be very bright. You want to avoid blowing out the rainbow. The key is a fast shutter to freeze the mist’s movement (it’s not as still as fog). Start with spot metering on the rainbow itself, then dial in –0.7 or –1 exposure compensation to keep the colors saturated. If the rainbow is weak, open aperture to f/5.6 but accept a shallower depth of field.

At dusk, you’re fighting fading light. The mist gets thicker and the rainbow more pastel. Drop to f/5.6 or f/4 to let in more light, and raise ISO to 400–800 – modern cameras handle that fine. Shutter will land around 1/30–1/60s, which needs a tripod. Handheld will blur the mist into mush. If you don’t have a tripod, brace against a tree or rock and use a 2-second delay.

Both times of day share one rule: expose for the rainbow, not the background. The mist will push your meter toward making the rainbow too dark. Bracket if you’re unsure.

The mist won’t wait – set it and shoot.