Selfoss and Dettifoss are a pair of waterfalls on the Jökulsá á Fjöllum river. You arrive at Dettifoss first. A short 10-minute hike or so leads to Selfoss.
I was driving like mad to get to this location, fearing we would be too late for sunset. We were, in fact, too late for Dettifoss. The waterfall was in deep shadow. The light was gone.
I figured we would have to come back the next day, but we took the path to Selfoss. Although Selfoss is lower in elevation, light from the setting sun had a clear path. The result was a magnificent rainbow, the best I have ever seen.
The light was quite bright, and a polarizer barely provided enough light reduction to smooth out the water.
I did not help matters one bit by shooting at ISO 160 instead of 100. It was an accident that I did not catch. Not wanting to overexpose the the highlights, I made a second mistake by underexposing the shadows. That would have helped smooth out the water as well.
Feature Shot Details: Canon 16-35MM F4 L lens at 24MM, ISO 160, F/16, 1/5 second.
Water on the rocks above is not from the river, it’s an accumulation of spray.
Details: Canon 16-35MM L lens at 16MM, ISO 160, F/16, 0.4 seconds.
The above shot is looking across the scene.
Details: Canon 24-105MM F4 L lens at 65MM, ISO 160, F/22, 0.4 seconds.
Shooting at F/22, as I did, is a mistake. That focal length is not as sharp as mid-range F-stops. From this distance F/11, focused on the waterfall would have been about right (there was no foreground to keep sharp). However, F/11 it would not have blurred the water like I wanted.
The solution, as I have mentioned before , is a set of neutral density filters. Polarizers can help, but you have to be careful in how they are rotated or they will obliterate the rainbow. A better choice would have been a neutral density filter. I now carry B&W ND filters of strength 3.0 (10 stops), 1.8 (6 stops), and 0.6 (2 stops). Six stops would have changed the exposure to 2 seconds or so at F/11.
Spray from Selfoss is intense, with emphasis on intense. You don’t exactly get soaked, but if the wind is blowing towards you, which it was for us, your lens will be covered with spray between every shot.
Have a box of lens cleaning tissues handy. Even though I wiped the filter between every shot, I spent a very long time in Lightroom removing spots caused by spray on the filter. Many shots were so covered with spray as to be unusable.
I also took some images with a Canon 14MM F2.8 L lens, capturing the complete rainbow plus more of the side waterfall. The images were beautiful except for one thing: The water looked awful (frozen, not silky), so I tossed the images in the digital bit bucket.
The problem was of my own making.
The 14MM lens does not take outside filters but it does take gel filters in the back, and I had them with me. However, I was not about to be fiddling around with gel filters with all that spray and with the light changing fast.
If you have a 14MM lens and are going to be photographing waterfalls, put the gel filter in ahead of time. For further discussion please see the section on the 14MM L lens in My Equipment List.
Rainbow Tips, Rainbow Math
The apex of a rainbow is 180 degrees from the sun. You will not see a rainbow looking towards the sun. If you see rainbows images that face the sun, they are fake. Here, you can see the light on the waterfall and the foreground rock. The rainbow is from sunlight refractions through the spray, just like a prism. There is no rainbow in the third image because camera positioning was at a right angle to the sun.
When looking for rainbows, make sure the sun is at your back. The lower in the sky the sun is, the higher the rainbow apex. At noon, depending on latitude, rainbows may be below the horizon, invisible. Thus, it is appropriate to consider terms like “rainbow rise” and “rainbow set”.
The huge, more than 180 degree arch in the second shot is because the sun is on the horizon and the foreground was below the horizon.
From an airplane, it is possible to see a 360 degree full circle rainbow.
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Up Next: North Iceland, Dettifoss Waterfall
Mike “Mish” Shedlock
