 Few sights in nature are as awe-inspiring as that of a healthy forest of giant kelp on a sunny day when the sea is calm and water conditions are favorable. On those days, when you slip below the surface you enter a magical kingdom where shimmering rays of sunlight dance through a golden undersea forest. Descend 20-30 feet (6-9 m) below the surface and you soon see the entire forest swaying back and forth in perfect rhythm with the ocean’s ebb and flow as waves roll gently overhead. Look up and you will see a golden canopy of floating fronds and leaf-like blades bunched together at the surface as flickering rays of sunlight illuminate the surface canopy, creating a natural kaleidoscope of captivating colors. While specialists tell us that more than 800 species of marine animals inhabit giant kelp forests, creating endless opportunities for underwater photographers, the kelp itself makes a wonderful photographic subject.
Giant kelp (Macrocystis pyrifera) requires sunlight to conduct photosynthesis so it can grow from the depths to the surface where the fastest growth occurs. The buoyant fronds of mature kelp are composed of three parts: a stem-like stipe, leaf-like blades and gas-filled spheres, or bladders, known as pneumatocysts. As the blades grow they split, and as they separate a number of gas bladders begin to appear near the base of the blades. The gas bladders provide buoyancy, enabling the kelp to float off the seafloor and grow upward toward the surface.
To the eyes of underwater photographers, the gas bladders and blades make excellent photographic subjects, often forming captivating geometric patterns as the kelp sways back and forth with the surge and movement of waves that pass through and over the forest. Creating a close-up image of the gas bladders and blades like the one pictured here requires the use of a macro, or close-up, lens and at least one strobe, or underwater flash.
You will want to maximize the depth of field or the area in front of the lens that is in focus. This requires the use of a small aperture, or f-stop, setting on the lens. A small aperture means that light from your strobe must strike the kelp and be reflected back into and through a small opening in the lens, but it can be confusing because a small aperture also means a higher f-stop number. In other words, you want to use as small of a lens opening as possible, which means an equally high f-stop number. Because a small aperture greatly limits the amount of light that enters the lens, you will probably want to set the power setting on your strobe to full power and place your camera and strobe close to the gas bladders. Position your strobe away from your lens, not directly next to the lens, to avoid lighting any out-of-focus particles that might be floating in the water between your lens and the kelp. That minimizes backscatter, the ruinous out-of-focus particles that create distracting blobs in underwater images. That is exactly what I did to create this close-up photograph of a group of giant kelp gas bladders off San Clemente Island, one of Southern California’s eight Channel Islands.
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