With springtime right around the corner, the weather in many areas, including here in the Pacific Northwest, will be ‘unsettled’, prime conditions for one of my favorite things: rainbows! Throughout the world’s temperate regions in fact, the change of seasons that is about to happen results in clashes of warm & cool air masses. That means frequent showery weather and a sky that’s often broken into clear and cloudy parts. When the sun is relatively low in the sky, whether morning or late afternoon, and there is precipitation in the area, you’ve got the perfect setup for rainbows.
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Some photographers turn up their noses at rainbows. I think I know why; they believe them to be ‘cliche’. But I don’t at all understand how anyone, photogs. included, could be cynical about something as beautiful as a rainbow. It’s true, I don’t like over-done subjects. And when a certain look or technique catches on (courtesy the internet), it tends to start looking gimmicky to me. But rainbows are one of nature’s wonders. So they will never be cliche to me. It is a small step from there to thinking that beautiful skies and light are cliche. And then you are well on your way to becoming a photographer of the grim. That’s not me!
I think it’s safe to say that most of us love rainbows. They are a beautiful way to add color and interest to any landscape image. And they are sufficiently rare as to always elicit a reaction whether viewing a picture or in person. So if you want to go chasing them, don’t ever let anybody make you feel less the photographer because of it. By the way, one of my followers requested this subject. So thanks Annette, it was a great idea!
This post will focus on standard rainbows, the kind that are formed by slanting sunlight hitting moisture-laden cloudy skies. I’ll leave oddball bows like moonbows, waterfall rainbows, etc. to another time.
How Nature Creates Rainbows
Before we get to tips, it’s helpful to know exactly how a rainbow is created. We aren’t going to get too sciency here, but optics are involved. Sunlight is made up of all the colors of the rainbow: red, orange, yellow, blue, indigo and violet (Roy G. Biv is how so many students have memorized it). When a beam of sunlight passes through a glass prism, as Isaac Newton first discovered, the light is split up and the colors hidden inside are visible to us. Normally they are all smushed together (that’s a science word I swear!). The colors appear because each one is bent at a slightly different angle as it passes from air to glass and back out again.
When big puffy storm clouds invade the sky, there are of course zillions of tiny water droplets inside the clouds. But high up in the clouds and even outside of clouds there are also ice crystals. Both water droplets and ice crystals can act like prisms, but as you might expect, the ice does a better job. That’s why rainbows are more common when there is a cool, unstable air mass creating tall, puffy and energetic clouds with cold, ice-rich tops. The reason why rainbows more often occur in afternoon than morning is because the atmosphere is more turbulent, with rapidly rising air forming ice crystals high in the clouds.
Rainbows are potentially visible to you when the angle between light source (sun), rainbow and you the observer is close to 40 degrees. This is because the light is bent (refracted) at a shallow angle when it enters the drop or ice crystal. It’s bent again once or twice more as it curves around and is concentrated on its way back to you. On it’s way through it is split into the colors of the rainbow. With ice crystals there is also reflection involved, which increases brightness and intensity. To check this out for yourself, play around on a sunny day with a water hose set on spray. Point it at varying angles with the sun to find the one that produces the best rainbows.
What does this tell us about chasing Rainbows?
I have caught plenty of morning rainbows, But combine the fact that the weather most often is suitable in late afternoon with the angle of 40 degrees and you can see that starting a couple hours before sunset is a great time to look for them.
When the sun is still fairly high, the triangle forming the 40-degree angle between the sun, rainbow and you is nearly vertical. As the sun gets lower, that triangle starts to lay down on its side. Then rainbows will not appear directly away from the sun but at an angle to it. And you are more likely to see partial and nearly vertical rainbows.
When you’re looking directly away from the sun, when that triangle is standing straight up, that’s when the classic rainbow with a full, tall arc will most often appear. When the sun is nearly set, you can still get full rainbows looking directly away from the sun. They’re just going to be very flat and shallow
So here are some tips for catching that rainbow!
- Be Prepared: When the weather is unsettled, when the weather-guessers are calling for thunderstorms, have your camera gear handy early and late in the day, with an eye to the sky at all times. Or just set aside time to go out and try your luck. Pay particular attention to the half of the sky away from the sun. Don’t forget raingear for both you and your camera; they don’t call them rainbows for nothing! Keeping your camera relatively dry and yet being ready for rainbows is a delicate, sometimes frustrating balancing act. But it’s worth it!
- Remember the Angle: Remember you get rainbows most often in the afternoon when the light makes an angle of about 40 degrees or less with the earth’s surface. So if you go out two or three hours before sunset, start by looking directly away from the sun. As the sun approaches the horizon, keep an eye out for partial rainbows at oblique angles away from the sun. For full rainbows that have a big arc, look an hour or so before sunset.
- Use a Polarizing Filter: To make the colors of a rainbow really come out, similar to what you observe with your eyes, use a circular polarizing filter. This will make a huge difference. In almost all cases, you want to rotate the filter so that the rainbow is at its most colorful. If you are very close to an especially large and colorful rainbow, you may want to minimize the color, either by leaving the filter off or rotating it only partway to max color.
- Composition is still Important: Sure a rainbow is a great subject on its own, but your composition will still make or break the image. Your foreground and background, how the rainbow cuts through the frame, how the other elements are situated in the frame, all of these things matter more than the fact you’re shooting a rainbow.
- Exposure is a Breeze (usually): Since the sun is over your shoulder shining front-light onto your rainbow and landscape, exposure is easy. You can even shoot in auto and get great results. Most modern DSLRs do a great job with the metering mode called Evaluative (Canon), Matrix (Nikon), or similar names. Even other metering modes work most of the time, but sometimes the rainbow is very bright and dark clouds are in the background, so there’s a chance of messing up your exposure. You could get underexposure if you point the center of your frame right at the brightest part of the rainbow or overexposure if you point at the darkest clouds.
- End of the Rainbow: Speaking of composition, you will do well to find an interesting element for the rainbow to come down to. This is particularly dramatic with partial rainbows, where there is a spotlight effect on something interesting, with the rainbow hitting ground very nearby and beautifully lighted (or dark and dramatic) sky and landscape beyond.
- Use the Rainbow as a Frame: With a full rainbow especially, using it to frame your entire image is a great idea. If it’s a partial, you can still frame your main subject, as I did with the image above and at bottom.
- Light Matters: Usually your light will by definition be good when it’s a rainbow day. But there are cases when the light is especially great and those when light is so so. Rainbow-making weather should make you think about going out and photographing no matter the time of day, but try to get to that great spot with the special composition very early or very late in the day. That way the light has a chance of being that much sweeter for the stronger composition.
- Chase that Rainbow! What mostly happens of course, is that a rainbow appears while driving or otherwise engaged. Then you find yourself trying to pull over and shoot it before it’s gone. This is a fine idea, but be safe!! My personal approach is to (as quick as is safe) drive, walk, run, somehow get to a spot where I have a decent composition, where the end of the rainbow comes down near something interesting. I don’t just stop and shoot it. I need to tell myself I don’t care about missing the rainbow, that the overall shot is the most important thing. So I miss a lot, but those I do get are better for it.
I’m wishing every one of you the best of luck catching all the rainbows that come your way. To return home from a shooting foray with a shot of a rainbow gives you a special little feeling, like you were given a sort of bonus or gift. Not quite as great as coming away with a pot of gold, but special nonetheless. Have a great weekend!