There are very few weather related events in nature to observe and photograph that can match the beauty and brilliance of the “elusive” rainbow. However, unless you live near a tropical rainforest, it is often difficult to locate rainbows, and when you do, trying to photograph them can be more than a bit frustrating!
One of the key factors in trying to photograph rainbows is attempting to predict where they might appear. Rainbows need two elements to develop; some form of moisture in the atmosphere, and sunlight. You can improve your odds drastically if you head out with your gear just before an approaching or departing storm, then look to find them displayed against the darkest part of the sky opposite to where the sun pops out. Unless you are a full time “storm chaser”, finding a rainbow is mostly a matter of being in the right place at the right time.
When photographing rainbows there are more than a few choices for composition, the most obvious ones being that you can photograph just the rainbow or incorporate the rainbow as an appealing element into your composition. The above image was taken from a helicopter over the island of Kauai, just after an intense thunderstorm passed over Waimea Canyon. Exposing for a rainbow is fairly simple. I tend to underexpose my shots to saturate the colors, especially if I am photographing with a dark sky as a background. Try using the exposure compensation feature on your digital SLR and dial in an exposure that is one to two stops less than your light meter is showing. Also, shooting in RAW format gives you ample opportunity to "tweak" the exposure and white balance later on when you are editing the images on your computer.
I always recommend that workshop participants use a tripod in the field, a practice that is especially true when photographing the elusive rainbow. Since rainbows often form in low light situations and since you will probably be using a smaller aperture to increase your depth-of -field, trying to merely handhold your camera can become a real exercise in frustration. Also, if you don’t already own circular polarizers (not the linear ones) I suggest you add them to your gear bag. By rotating the filter in the mount you can actually intensify the rainbow effect. However, spoiler alert, if you rotate the filter too much and you can actually eliminate the rainbow!
Rainbows can also be seen in the surf of ocean waves and in the spray of waterfalls. The above “spray rainbow” shot was taken on the coast of Oregon, and like the rainbow over Kauai, it only appeared for a short time. However, spray rainbows are more predictable than sky rainbows because they have a continuous source of moisture.
You may not find the proverbial pot of gold at the end of the next rainbow, but now you may have a better chance of creating a golden opportunity to capture a memorable rainbow image on your next outing.
Stay focused and happy shooting!!