How to photograph a rainbow
Rainbows give you five to thirty minutes, usually with wet hands and a wind-whipped jacket. Here is how to be ready: where to stand, what to set, and the one filter that can double a rainbow or delete it.
First: be there before it appears
A rainbow needs three things at once: direct sun behind you, rain in front of you, and the sun less than 42 degrees above the horizon. That combination is most common when a shower is just clearing: observational studies found that around nine out of ten rainbows appear in the hour right after rain stops. So the moment to grab the camera is not during the downpour but the minute the sky brightens while it is still raining somewhere nearby.
Bowcast's live map does this waiting for you: it scores the next hours and days for sunlit-rain conditions around your exact location and points at the best window, so you can plan a shoot instead of gambling on one.
Where to stand
- Sun at your back, rain in front. The bow always forms directly opposite the sun, centered on the shadow of your own head.
- Lower sun means a taller bow. Near sunrise or sunset the arc stands almost a full semicircle; near the 42 degree limit only a low sliver hugs the horizon. Golden-hour rainbows are also warmer in color.
- Look for foregrounds in advance. Since you know a bow will appear opposite the sun, you can scout the composition before it exists: a lighthouse, a lone tree, a ridgeline where the arc will land.
Camera settings that work
- Underexpose slightly (about -0.3 to -0.7 EV). A blown-out bright sky erases the bow's color; a touch of underexposure saturates it.
- Aperture f/8 to f/11 for depth across the landscape; the bow itself is at optical infinity.
- Keep ISO low and let shutter speed float; there is usually plenty of light on the sunlit side of a clearing shower.
- Go wide. A full bow spans about 84 degrees of sky: even 16-24mm on full frame barely contains it. No wide lens? Shoot a panorama sweep and stitch.
- Shoot RAW. The subtle outer bands and the darker sky between a double bow (Alexander's band) survive editing far better in RAW.
The one filter that changes everything: a circular polarizer
Rainbow light is strongly polarized. Turn a circular polarizing filter (CPL) one way and the bow's colors deepen dramatically, far beyond anything you can add in editing. Turn it 90 degrees the other way and the rainbow vanishes from the frame entirely: the fastest way to lose the shot without noticing. Rotate while watching the bow, stop where it is strongest, and check the corners on ultra-wide lenses, where polarization can be uneven.
- Any reputable CPL sized to your lens thread works: the effect is physics, not brand magic.
- A tripod helps at golden hour, when the best bows happen and light drops fast.
- A microfiber cloth is non-negotiable: you are, by definition, photographing near rain.
Beyond the single bow
- Double rainbow: look about eight degrees above the main arc for the fainter secondary with reversed colors. Expose for the primary; the secondary rides along in RAW.
- Supernumeraries: delicate green-violet fringes just inside the main bow, produced by small, uniform drops. A gift: shoot everything.
- Red rainbow: minutes before sunset the bow can turn almost entirely red. Combined with its maximum height, this is the trophy shot.
Know when it's coming
The pattern to internalize: evening shower, brightening west. When rain is easing and the low sun breaks through behind you, turn around. Or skip the internalizing: open Bowcast, and it will tell you the hour, the direction is always the same: opposite the sun.
Next: the places on Earth where this happens several times a week →