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IMAGING PHOTO TECHNIQUES A DIFFERENT LIGHT USING LED LIGHTING FOR UNDERWATER STILL PHOTOGRAPHY Text and photos by Andy and Allison Sallmon Not long ago, underwater shooters were largely divided into two camps: still photographers and videographers. This factional division was based on practicality more than argument — cameras were dedicated to either still or video imaging, and, given the associated costs, it made sense to pick a side and stick with it. In more recent years, however, the lines have blurred. Most cameras now feature both still and video capabilities. Many topside photographers and videographers have LED lighting works very well for closefocus, wide-angle images with small- to medium-sized foreground subjects such as this cabezon, as it is already necessary to get close to the subject. embraced this versatility, but adoption has been slow in marine photography because of the particular lighting needs of underwater shooters. Historically, underwater still photographers have carried strobes, which use capacitors to provide a momentary burst of light when the camera’s shutter is triggered. While some strobes have built-in continuous light functionality, these were more often used for aiming or assistance during night dives rather than emitting constant light bright enough to allow high-quality video imaging. At the same time, dedicated underwater video lights did not produce enough light to 102 | WINTER <strong>2016</strong>
allow consistent, high-quality still photography. And carrying both types of lighting meant lugging around an inordinately bulky rig. Recently, however, developments in LED (light-emitting diode) technology have allowed high-output, compact lights to become mainstream. At last, underwater shooters have access to light systems that can support both still and video imagery. FEATURES OF LED LIGHTS Characteristics used to describe LED lights include lumen rating, burn time, beam angle, color-rendering index and color temperature. All must be considered from a practical standpoint when selecting a light for underwater still photography. Some units are tested according to the specification for flashlight performance issued by the American National Standards Institute and the National Electrical Manufacturers Association (ANSI/NEMA FL 1-2009 standard), which certifies that a light will perform as intended (e.g., an FL 1-compliant light is guaranteed to maintain its full lumen output throughout its burn time). The lumen rating defines the amount of visible light emitted. In other words, this rating gives you the best indicator of an LED light’s power. While a few options exist that provide an output similar to strobes (8,000 lumens or more), for now the price tags of LED lights with this level of performance will deter many photographers. A light’s lumen rating represents its output at the highest power setting, so choosing a lower power setting decreases the light output proportionally. This may also affect a light’s burn time (or run time), a characteristic that describes how long the light will last at a specific lumen output, usually the light’s maximum, until it reaches 10 percent of the initial output measurement. Beam angle is the angle at which the strength of the beam is half of the light’s maximum strength (the maximum strength is generally at the center). This is also known as the full-width at half-maximum (FWHM) potential. This represents one of the key differences between high-end strobes and LED lights intended for video use. Strobes, which are used to capture a momentary portrait or behavior, generally have a wider beam angle (110–120 degrees is common) than do LED lights (typically less than 100 degrees) since video is commonly used to capture dynamic subjects. Complicating this issue is the refractive index of water. When lights with flat lenses are submerged, the beam angle is reduced by as much as 33 percent, but many manufacturers report only the topside beam angle, which can confuse potential purchasers. A few manufacturers have made an effort to simplify matters by measuring and reporting the underwater beam angle; others have designed lights with a domed lens to eliminate this complication altogether. Color rating, also known as color-rendering index (CRI), defines a light source’s ability to accurately depict the color spectrum compared to an ideal reference light of the same color temperature. CRI is expressed on a scale from 1-100; the higher the number, the more accurately colors will be reproduced. It is generally thought that a CRI of 90 or above is desirable for professional-level topside imaging. CRI is distinct from color temperature, expressed in degrees Kelvin, which characterizes light as warmer/yellower (lower values) or cooler/bluer (higher values). Most manufacturers From top: Using lights of differing strengths works well to achieve interesting shadows for macro subject matter such as this Spanish shawl nudibanch. Small, light-colored creatures such as this cowrie make good macro subject choices when shooting with LED lights. Wide-angle photography in bright, clear water might require shooting toward midwater as opposed to shooting upward toward the sun. This octopus shows that smaller subject size ensures that photographers are less limited by relatively narrow beam angles. ALERTDIVER.COM | 103
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