The mountain landscape of Denali National Park is conducive to scattered rainstorms during the summer months. This results in many rainbows, but this particular one continued to grow in intensity. It was so bright that it seemed it would explode. I shot this scene with a 500mm telephoto to focus on the band of color hanging over the spurce trees scattered across the tundra. A polarizing filter can be used to increase contrast and saturation in a rainbow, but none was needed or used in this case.
Canon 1Ds Mark III, 500mm f4L IS, 1/320 sec @ f8, ISO 400