The Lake Superior Sea Cave was almost pitch black inside at sunset. John set up three Canon 600EX-RT Speedlites each with 1/2 CTO gels on them and determined the exposure for the inside of the cave. Using automatic flash metering, he decided on using FEC +2 for the cave. Then he slowed down the shutter speed until the evening sky looked pleasing. As the western sky darkened, he slowed the shutter speed. Here, setting the flash exposure first makes sense because the ambient light exposure steadily diminishes. Canon 5D Mark III, 24–105mm at 35mm, ISO 640, f/16, 1/3, Cloudy WB, +2 FEC.