Using Video Lights

By Mark Jamieson

Light is the single most important component for producing good underwater video. Whether you make use of natural sunlight, artificial light, or a combination of both, you'll want to understand how to make use of each light type in order to achieve the best results possible.

While your main source of light will be sunlight in most situations, you can't control the sun's brightness or direction. You can, however, control your camera's position in relation to it. When shooting using sunlight as your primary light source you'll want to position yourself in relation to your subject so that the light appears from a direction over your shoulder.

There are many situations where your camera cannot be positioned in this fashion and natural sunlight will not work to your advantage. In addition, if you plan to shoot video of close-up (macro) subjects, within a shipwreck, cave, or while night diving, sunlight will not be available or will not work to your advantage. In these situations, you'll want to use video lights.

Video lights are also extremely useful when shooting video in normal daylight conditions and can be used to:

• Enhance the sharpness and natural colors of your subjects.
• Add fill light when shooting subjects that are backlit or in the shadows. Fill light is lighting the shadow areas to reduce the overall contrast between highlight and shadow areas of a scene.
• Improve the overall quality of the video you shoot at deeper depths.

When you descend to deeper depths, the level of natural sunlight diminishes and the color and contrast of your underwater subjects is reduced. While most camcorders can easily record images under low light conditions, the color saturation and quality of the video image decreases, appearing more grainy as the camcorder increases its automatic gain setting to compensate.

Note: If you normally use a color correction filter in front of your lens when shooting video with available sunlight, you'll want to remove it before shooting with video lights. Otherwise, your video footage will have an overall colorcast.

Video lighting options

There are two primary types of underwater video lights you can use with your video housing:

• Quartz Halogen (Tungsten)
• High Intensity Discharge (HID).

Each light type has particular characteristics as well as pros and cons.

Halogen lights contain a tungsten filament similar to a household light bulb and produce a warm yellowish-toned light (3200-3400 K) when compared to the color temperature of sunlight. If you plan to shoot video using both quartz halogen lights and sunlight you'll want to do one of the following:

• Set the white balance setting on your camcorder to an indoor setting or perform a manual white balance using a white card that is illuminated by the halogen lights. When shooting wide-angle video, the region beyond the area illuminated by your video lights will appear more blue in color depending on the intensity of your halogen lights and the natural available light. If you're shooting close-up (macro) subjects, balancing the foreground and background light will generally not be of concern.
• Add color correction filters to the front of the halogen lights so that the color temperature of their light output matches that of natural sunlight. You can then set the white balance setting on your video camera to the outdoor setting so it matches the color temperature of sunlight or manually white balance your camcorder using a white plastic card that is illuminated by the filtered lights.

Note: Adding color correction filters to color balance video lights reduces their intensity.

High Intensity Discharge (HID) lights contain a capsule of metal halide gas that's trapped within the light bulb to which an electrical current or arc is applied causing the gas/metal combination to glow. An HID light emits a very bright white light (5500-6500 K) that closely matches the color temperature of sunlight.

White balancing your camcorder between HID lights and sunlight is generally not an issue when shooting using normal or wide-angle optics making HID lights particularly well suited as fill lights. You simply need to set your camcorder's white balance to the outdoor setting or manually white balance using a white plastic card that is illuminated by the HID lights.

HID video lights take a few moments to achieve their full brightness when they are first turned on so you'll want to anticipate this when the subject of a lifetime presents itself. HID lights are more energy efficient compared to their halogen counterparts. The light emitted from a 10 watt HID light source easily exceeds the brightness and penetration of an equivalent sized 30-watt quartz halogen light. HID lights also maintain a consistent brightness and color temperature as the remaining power in your battery pack drops unlike what occurs with quartz halogen lights. HID light bulbs generally have a service life that is10 times longer than quartz halogen light bulbs.

Mounting and aiming video lights

While you can get away with using one video light for fill lighting situations, you'll normally achieve better results when using two lights. Two lights produce a more even illumination than one light alone and each light will balance the shadows that are cast by the other. You can also use one light as the primary light source known as the key light, and the second as a less intense fill light.

Most camera housings are equipped so that video lights can be mounted directly on a set of flexible arms that allow the lights to be positioned above and on either side of the housing. Mounting the lights so that the light shines from above serves two purposes:

• It naturally simulates how subjects are lit by sunlight. When light is cast from above, the resulting shadows are cast downwards. Since sunlight appears from above when you're underwater, having the lights positioned in this fashion simulates how natural light appears. There is nothing preventing you from experimenting with other lighting angles (that is, lighting from below, to the side, or from behind), but this technique generally works best in most situations.
• It helps to minimize the amount of backscatter that appears in the image.

Backscatter occurs when the tiny particles of matter suspended in the water between your lights and subject, reflect light back towards the camera lens like thousands of tiny reflectors. Your video appears as if it were shot in a snowstorm. Backscatter is particularly troublesome when the water is turbid and your video lights are not aimed correctly and is particularly bad whenever your video lights are positioned so that they point directly forward at the same height as the lens.

To minimize backscatter, you should set your video lights so that they are spread apart as wide as possible, pointing downwards towards your subject from roughly a 45-degree angle. They should be aimed so that the outer edges of the light beams intersect on your subject with a minimal amount of overlap. This ensures that the lights illuminate only your subject and not the region of water in the foreground between your lens and subject, reducing the possibility for backscatter.

Aiming your video lights so they have a minimal amount of overlap also provides the widest swath of light possible - which is useful when you're shooting wide angle - while at the same time, minimizes the chance of a bright hotspot appearing in the center of the overlapping area.

Controlling the brightness of video lights

When using video lights in combination with natural sunlight, your goal should be to complement the sunlight that appears underwater, not use the lights as a substitute for sunlight. In doing so, your scenes will appear more natural.

Video lights are most effective at medium close and close distances. For that reason, your lighting will appear most effective when you're close to your subjects. When shooting wide-angle video you should expect that only the foreground areas of your scene receive light. It's not realistic to expect that standard video lights have enough power to light large subjects such as a shipwreck.

The easiest way to control the brightness of the video lights on your subjects is to change the distance between the lights and the subject by moving them towards or away from the subject in relation to the video housing.

You can also control the intensity of video lights by attaching neutral density filters to the light's front. These grey-colored filters reduce the intensity of light without changing its color. They can be purchased in varying opacity levels and allow you to control the intensity of light without otherwise changing the exposure settings on your camcorder.

If your camcorder and housing combination provides manual exposure capabilities, you can adjust the exposure setting on the camcorder so that the subject appears correctly exposed when illuminated by the video lights. If it is also equipped with a feature called Zebra, you may want to turn it on. This feature graphically displays a diagonal line pattern in the viewfinder wherever the highlight areas in your scene are overexposed.

Manually adjusting the camcorder's exposure setting to correctly expose for the lights will affect the brightness of any background areas of the scene that are not illuminated by the video lights. For example, the background will appear darker as sunlight diminishes even though the video lights provide a constant illumination for the foreground. If the ratio between sunlight and artificial light provides too much contrast between the foreground and background illumination in your scene, it may appear as if it were shot at dusk. In those situations, you'll want to use some of the above techniques to balance the light illumination with the available sunlight.

You can experiment with various light and camcorder setting combinations and note which arrangements give the best results for close-up, medium, and wide-angle work, under a variety of conditions. You can then record the settings on a plastic dive slate you can attach to your housing for quick reference.

Precautions when using video lights

Video lights are designed for use under the harsh environments that are normal to diving, but should be treated with the same respect you would treat any piece of electronic equipment.

Collapse the light arms against the housing whenever you enter and exit the water so the lights do not accidentally get jarred out of position and hit the housing, front dome port, or you. Be mindful of the lights when carry your camera system topside so you don't accidentally strike someone as you carry your video system around on the deck of the dive boat.

Video lights, particularly HID lights, produce an intense bright light, so you should avoid staring directly at them for a prolonged period of time to avoid injury to your eyes.

The bulb elements are particularly vulnerable to damage immediately after they are shut off, until they've had a chance to cool. Do NOT:

• Handle the light roughly until it has cooled sufficiently.
• Replace a bulb until it has cooled sufficiently.
• Touch the glass on a bulb with your bare fingers when installing or replacing it.
• Replace a bulb when the light is powered on.

Practicing your underwater lighting techniques under a variety of conditions and learning from your mistakes will help to ensure you become a master videographer with your particular video system.