Manufacturers of underwater photo gear constantly strive to make technological and ergonomic advancements that help you capture images beneath the sea. Some are gimmicks; some aren't. Here are a few I highly recommend you take a closer look at:

Ikelite's amphibious digital light meter is the first to measure both strobe and ambient light.

What It Does - The first amphibious digital light meter capable of accurately measuring both strobe and ambient light.

Why You Need It - For years, the industry standard has been the Sekonic Marine Meter II, but it measures reflected light only and is powered by hard-to-find mercury batteries. The Ikelite digital light meter is clearly the new industry standard.

Usage Tips - There are two different sensors on the meter: an incident light sensor that can be used for both ambient and strobe light readings, and a reflected light sensor that is specifically used for measuring the available light on a scene. Here's how to use them:

• Turn the meter on. It seems obvious, but since the meter automatically shuts down after 5 minutes if not in use, you will frequently need to restart. An LED display screen will light up.
• Set meter according to film ISO. Decide whether you want to measure strobe light or ambient light, and set the mode accordingly. Assuming you want to measure ambient light, there are two choices. A reflected light sensor on the back of the meter measures the light in the direction the meter is pointed. The incident light sensor is on the front behind a white dome, and it measures the light falling on the meter. A full explanation of when to use ambient versus incident light is beyond the scope of this article, but suffice it to say that this meter does both quite well.
• Position it. When the strobe mode is properly set, place the meter at the preselected strobe-to-subject distance and test fire the flash toward the meter. The digital LED will read the proper f-stop.

For More Information - Call (317) 923-4523.

Subal's over/under split diopter corrects the problem of differing amounts of light and focus points in over/under shots.

What It Does - The split diopter is a useful tool for shooting over/unders, images that incorporate both a topside and an underwater view on the same frame.

Why You Need It - The over/under shot is best done with a wide-angle lens on a housed topside camera. The water interface is usually in the middle of the frame, but the amount of light transmitted and focus point is different for the above portion than for the underwater portion. The split diopter corrects for this.

Usage Tips - Using a wide-angle with a housing requires the use of a dome port to avoid vignetting and optical aberrations at the edge of the frame. However,

• A dome port introduces a virtual image. The virtual image typically occurs at a distance twice the diameter of the dome, and if the lens can't focus on the virtual image, it can't focus at all. For example, if an 8-inch dome is used, the virtual image is about 16 inches away. The lens must focus to 16 inches to account for the refractive index of water and the virtual image. This is usually too close for the topside portion of the frame. Usually about a +4 diopter close-up lens is utilized to enable the lens to focus on the virtual image for the underwater scene and still hold the distance setting required for topside.
• The other half of the problem is that light is absorbed when it passes through the water, so there is more light topside than under water. The split diopter solves this by mounting a neutral density filter (usually two stops) in the top portion of the filter.
• The Subal split diopter comes in a 77mm filter size, but offers adapters for different size filters.

For More Information - Call 800-480-8333.

The Seacam Swivel 45 viewfinder is ideal for taking shots of sedentary fish, macro subjects and over/unders.

What It Does - Allows the photographer to focus using an enlarged prism from a 45-degree angle and swivel the finder 360 degrees.

Why You Need It - Actually you may not need this viewfinder for everything, which is why it is easily interchangeable with the standard magnified viewfinder. If I were shooting fast action with a wide-angle lens, something like humpback whales or a shark feed, I would stick with the standard finder. (Viewfinders have double O-ring seals and are held in place with a retaining ring, eliminating the need for tools when changing). However, with sedentary fish, macro subjects, and over/unders, this new S45 viewfinder presents an amazing advantage.

Usage Tips - The mask comfortably rests in the 45-degree eye cup, and if the composition is vertical, it will quickly swivel to the appropriate side.

• There is a +/-3 diopter correction in the viewfinder, so divers with corrected vision can customize accordingly.
• The magnified view is nearly 1:1 life-size, making it extremely easy to read the LED display at the bottom of the camera's viewfinder.
• The housing offers a wide variety of ports for most of the popular lenses used in underwater photography, including a 9-inch mineral glass dome perfect for capturing over/unders.
• Seacam housings are available for a variety of cameras including the Nikon F5, N90S, 8001, and N70; Canon EOS series (1N, 5, 500/500n, 1000, 100), and a number of Minolta SLRs as well.

For More Information - Call (305) 451-3737.

Sea and Sea's cordless through-the-lens slaves: The YS-30 (left) is perfect for close-up and macro use and the YS-90 (right) is a primary strobe as well.

What It Does - Cordless TTL (through-the-lens) slave.

Why You Need It - Most slave strobes operate only on a manual power setting-either full power, or some preset fraction thereof, like half or quarter power. The Sea and Sea YS-30 and YS-90 each allow cordless TTL operation when used in conjunction with a primary TTL strobe, a significant advantage to TTL enthusiasts. The primary strobe fires and quenches according to its TTL protocol, while the cordless slave reads the light, fires and also quenches with TTL automation.

Why You Need It - Finding a way to trigger a second strobe in the TTL mode has long vexed photographers who depend on autoexposure control. These cordless slaves are handy solutions to the need for multiple strobes and provide the ability to work with automatic exposures. The YS-90 serves as a versatile, full-featured primary strobe as well, while the YS-30 is excellent for close-up and macro use.

For More Information - Call (760) 929-1909.

Ikelite's remote through-the-lens slave sensor is perfect whether you're working in the high ambient light of a shallow reef or in a pitch-black cave.

What It Does - The Ikelite remote TTL slave plugs into any Ikelite TTL strobe where the synch cord would normally go. The separate sensor can be swiveled so it points towards the primary light. A knob on the back controls the sensitivity of the slave sensor. The Ikelite remote sensor reads the amount of TTL light emitted from the primary strobe and the TTL camera reads the light from both strobes passing through the lens and automatically signals the strobes to quench when the exposure is correct.

Why You Need It - Like the Sea and Sea YS-30 and YS-90, the Ikelite remote sensor provides for cordless TTL slave lighting. The fact that the sensor can be swiveled to optimally face the primary light, and the variable sensitivity control make this a valuable tool whether working in the high ambient light of a shallow coral reef or within a pitch black cave system.

Usage Tip - Ikelite recommends a +1 stop realignment on the film speed dial for remote TTL work. For example, with an ISO 100 film, set the dial to ISO 200.

For More Information - Call (317) 923-4523.

Aqua Vision Systems cords and adapters allow photographers to disconnect and reconnect a camera and submersible strobe under water while maintaining TTL capability.

What It Does - A wet connector system allows a camera and submersible strobe to be connected and disconnected while under water. For many years photographers have been shooting with E-O cords, but they require fully manual exposures. A system of wet TTL cords and adapters allows this same convenience to reconnect under water, but maintains TTL compatibility between the camera and strobe.

Why You Need It - Whether the need is for a different perspective or simply more shots per dive, often two or more cameras are carried below. Carrying separate strobe systems for each camera is potentially very expensive, and unless assistants are available to schlepp gear, very cumbersome. A system of wet TTL connectors allows the use of multiple cameras with a single strobe, yet still maintains exposure automation.

Usage Tip - The Aquatica system of wet TTL connectors provides a variety of configurations, including bulkhead connectors for housings (female), direct synch cords for Nikonos strobes (male), converters for all brands of standard Nikonos TTL strobe cords (male), and pigtail connectors (female) to standard Nikonos V TTL fittings.

For More Information - Call (514) 737-9481.

This buoyancy arm and RS tray from UltraLight Control Systems provide support for arm-weary underwater photographers.

What It Does - Some underwater cameras, particularly the Nikonos RS, are notoriously heavy, even under water. Holding them for a long period of time can cause fatigue, discomfort, and actually some physical maladies not unlike tennis elbow. The buoyancy arm provides some positive lift to the system, thereby alleviating the fatigue factor.

Why You Need It - For those who find their forearms aching at the end of the day after holding their cameras motionless for long periods of time waiting for the fish to behave just right, buoyancy arms may be a salvation.

Usage Tip - For Nikonos RS users, see the UltraLight RS tray pictured here. The padded curved support rests against the back of the right hand, supporting it while still allowing ease of shutter release.

For More Information - Call (800) 635-6611.