Focus Lights for Underwater Photography

A focus light is a critical tool for photographing macro critters or when shooting in dim environments

By Joseph Tepper

Light is at a premium underwater. We have strobe lights to illuminate large scenes and bring back color and contrast to subjects. Continuous lights measured in the thousands of lumens are powerful tools for shooting video. But there’s one light source that often gets overlooked: a proper focus light.

What Is a Focus Light?

In short, a focus light is any continuous light that helps your still photography camera achieve focus as quickly as possible. For the purposes of this article, a focus light is different than a modeling or target light. Modeling lights are frequently built into your strobes and exist—in theory—to show you where the light is aimed. However, as strobe positions vary dramatically based on camera orientation, environmental conditions and creative lighting, these modeling lights will rarely actually be pointed directly at your subject. 

On the other hand, a focus light is a dedicated tool that is aimed at the subject so that your camera—be it a compact or DSLR—can quickly lock focus. Modern focus lights for underwater photography typically range in output from 600 to 2,000 lumens and offer both spot and wide-beam modes. As well, some more expensive models have multiple color modes: white (standard), red (helps focus without frightening skittish fish), and blue (fluorescence photography). 

That said, there are other options other than a “dedicated” focus light. Dive torches are typically less powerful and only offer a narrow beam, but they will perform as a focus light for macro photography in a pinch and are quite common. A more powerful continuous light for underwater videography (2,000–5,000 lumens) will offer more than enough output for use as a focus light.

The shadows created by these mangroves necessitated the addition of a centrally-mounted focus light

A torch can work both as a focus light and as a video light, as seen in the system above

Do You Need a Focus Light for Underwater Photography?

So, do you really need a focus light for underwater photography? In short: yes. If you’re taking images of medium (8–16 inches), macro (1–8 inches), or super-macro subjects (less than one inch), then your camera’s autofocus system will benefit from the addition of a focus light. This applies even in broad daylight: Many cameras use so-called contrast detection to achieve focus and without the added light may not get pin-sharp focus or take too long to do so. 

The need for a focus light is exacerbated in dim conditions such as early or late in the day, in semi-covered environments, or (of course) during night dives. For macro photography, the shadow of a ledge or overhang is enough to make your camera’s autofocus struggle unless you add some continuous light. Even wide-angle photography demands the use of a focus light in environments such as inside a shipwreck, during a wall dive with the sunlight coming from behind the subject, or at dusk.

There are certain types of underwater photography that do not require the use of a focus light such as surf, water-sport, or freediving photography. These types of images are taken in the shallows, with plenty of sunlight, and adding a focus light will also add bulk and drag to the setup.

Focus lights aren’t just for macro photographers: Without added continuous light, dim and dark dive conditions can pose a challenge for your camera’s autofocus

Choosing a Focus Light

“Can I use my strobe’s modeling lights as focus lights?” This is a common question for those looking to invest in another piece of gear. These lights were not designed to be focus lights, as they are not powerful and are rarely aimed directly at the subject—if using proper strobe positioning. They may work as a backup if your focus light were to die during a night dive, but any serious shooter will want a dedicated focus light.

There are many options out there—from slim, compact torches to large, dual photo-video lights. Equipment brands that produce focus lights include i-Divesite, Fantasea, Light & Motion, Kraken, and FIX Neo. Your housing manufacturer may even produce a proprietary focus light. 

Choosing a specific focus light comes down to budget and how you’d use it. You can purchase a compact, mountable focus light that can work as a dive torch for well under $100. However, such a light will likely only have one power setting and one button. Other mid-range focus lights ($100–$400) begin to offer multiple power and color outputs. High-end focus lights ($500–$800) have advanced features such as LED displays for battery and output. At the end of the day, it’s important to remember that any dedicated focus light—be it a $50 pocket torch or $800 dual photo/video light—is better than none at all. 

There’s a large number of focus lights available on the market at a variety of price points

Focus Light Mounting Options

The most popular way to mount a focus light on an underwater camera system is directly on top of the housing. Most housings have a “cold shoe,” which is a mount shaped after the “hot shoe” on many cameras where you’d attach a flash. For underwater photography purposes, the cold shoe can be used to add a variety of accessories. You’ll need a cold shoe adaptor to mount your focus light—although other items such as a clamp or ball adaptor to your light may be needed as well, so make sure to consult your equipment provider. 

There are several benefits to mounting your focus light on the cold shoe. Its central location makes it possible to turn it on and off with ease and make small adjustments in positioning if needed. The vast majority of the time, however, the central location will mean the focus light is automatically aimed at the subject. This means that your focus light almost becomes a secondary thought—an important aspect when you’re already worrying about strobe positioning. 

Some housings don’t have a compatible cold shoe on top. In this case, an alternative mounting method is to use a triple clamp to attach the focus light to the same ball adaptor as your strobe arm. This is also a popular choice for the versatile shooter: By mounting two powerful continuous lights on each handle via triple clamp, you can alternate between using them as properly positioned focus lights for still photography and as full-fledged video lights.

Mounting the focus light to the cold shoe is the simplest solution for shooters only taking still images

Mounting the torch via a triple clamp or additional strobe arm lets it function both as a focus light for stills and an easily positionable video light

Using a Focus Light for Underwater Photography

Using a focus light for underwater still photography is fairly self-explanatory. However, your exact operation will depend on the model. For example, if you’re using a high-powered light that only has a burn time of 40 minutes and you’re planning on a longer dive (or multiple dives), consider reducing the output to increase the burn time or be sure to turn it off between subjects. 

One concern new users of focus lights have is the impact of the torch on their image exposures. While focus and video lights have increased in power, they are no match for the light-absorptive properties of water and lack the intensity of your strobes. So, as long as you’re shooting at a fast shutter speed (above 1/100s) and closed aperture (greater than f/8), your focus light should have no impact. If you are seeing a hotspot—which is most likely to happen at night when there’s little other ambient, continuous light—then just increase the shutter speed to eliminate it without impacting the strobe exposure. 

Conversely, advanced photographers use continuous lights to great effect to add creative lighting in their images. Not only do these invaluable pieces of gear aid your camera’s autofocus, but they can also be a tool to add spotlighting, back lighting, and texture to your images.

Diving in wrecks often demands the addition of a focus light for easy camera focusing

Some more advanced models offer a “red mode,” which is believed to be less startling to skittish subjects

Final Thoughts

New underwater photographers are often advised to invest in a pair of good-quality strobes. The same goes for a focus light, which will eliminate the any frustration when trying to focus on macro critters or dim conditions. You can step it up a notch by using a higher-powered light designed for videography or creative still photography lighting. 

More than just a focus light: Use your focus light to create special lighting effects, such as this spotlit octopus