Strobe positioning is one of the continuous challenges of underwater photography. It is the most critical element of each photo after dialing in the basic camera settings. Proper strobe positioning will light the subject in a way that makes the colors pop, create depth through shadows, aid the camera’s auto white balance calculations and minimize backscatter.
So no pressure to get it perfect, right?! ;- )
If you haven’t yet, be sure to read my article How to Minimize Backscatter, as understanding backscatter is a prerequisite to determining effective strobe positioning.
Underwater strobe positioning can be broken down into 4 main categories: macro and wide-angle with a single strobe, and macro and wide-angle with dual strobes. Note that positioning video lights (for video or still photos) follows all these same rules.
The Objective of Strobe Positioning
Our goal is to light the subject, bringing back the rich colors lost as we descend through the water column, while also minimizing backscatter. The three steps in this process are pointing the strobes so that they light our subject, adjusting the power of the strobes for proper exposure (unless you’re shooting TTL / automatic), and then subtly adjusting the positioning to minimize backscatter.
It’s imperative to think about these steps even before shooting the first frame. My process is to spot the subject and envision the shot I would like to create, along with the angle I will be shooting from. Next, I’ll adjust camera settings to where I expect they will need to be. I’ll then adjust strobe power and position the strobes to where I also think they will need to be. Only then do I slowly move in to compose the shot and actually look through the viewfinder or LCD screen. This method ensures that you’ll likely only be required to make small adjustments as you fine tune the shot. It’s a very deliberate process because we’re creating a photo, not just snapping the shutter a few times before swimming off.
Underwater strobes produce a cone of light with beam angle of roughly 100 degrees. And we already know that we want to illuminate the subject while minimizing the amount of light flashing through open water (to minimize backscatter). As a result, our strategy is to use the edge of the strobe’s beam of light to illuminate our subject or scene.
Wide-Angle Strobe Positioning
There are three concepts to remember for wide-angle strobe positioning. The first is to keep your strobes (or strobe) behind the back of the dome port. This is essential in order to prevent strobe light from directly hitting the dome port and creating some nasty flare.
The second is to position your strobes wide and far from the housing for subjects that are farther away (e.g. manta rays, sharks or reefs) and to position them closer to the housing for closer subjects like fish.
The third is to angle the strobe heads out. This ensures that only the inside edge of the beam of light (the cone of light) reaches the subject. Since only this edge of light is illuminating the subject, the water between the dome port and the subject is not lit, minimizing backscatter.
Below are some tips for precise strobe positioning.
Strobes Even with or Slightly Above Lens
We are used to the topside world where the sun makes shadows fall beneath features, so it’s natural that we try to reproduce this underwater. Keep strobes even with the lens or slightly above the lens so that any shadows fall below the subject features. When the opposite occurs you’re left with an eerie Halloween-like effect.
The only exception to this rule would be something like sharks swimming mid-day in clear water (a strong ambient sunlight scene). In a situation like this, you may choose to have the strobes below the camera lens since your goal is not to light the shark, but to fill in the dark shadows underneath.
Make Small Adjustments
Remember that a small adjustment in strobe position will create a larger effect at the distance of your subject (think of looking through binoculars, where 1cm movement can move your field of view by ten meters). Start with very small adjustments, making sure to review the image in the camera’s LCD after each shot.
Portrait Orientation – The Same Rules Apply
All the same strobe positioning rules apply when shooting in portrait orientation. If you simply rotate your housing 90 degrees, then one strobe will be directly below the subject creating unnatural shadows (and often a hotspot). When rotating your housing, make sure to move your strobes so that they are again on the sides of your housing.
Single Strobe Lighting
When lighting a wide angle scene with a single strobe, we generally want to keep the strobe above the housing and slightly to the side of the subject we want to emphasize (think 11:00 or 1:00 position). This position keeps the light fairly centered in order to avoid drastic shadows in one direction, but still produces enough shadows to create depth.
If a fish or say, a shark, is swimming left to right through the frame, positioning the strobe towards the right side of the housing will shed the majority of the light on the subject’s face. If the coral is on the left side of the composition, positioning the strobe on the left side of the housing will light the coral without lighting up all the water in the remaining 2/3 of the frame.
Rules are made to be broken, right?! Try moving your strobe(s) to the top of the housing or any place that that might create a dramatic lighting effect on the subject.
If you haven’t moved your strobe(s) much to date, the first thing to do on your next dive is swing them all the way to one side and then all the way to the other. Get the strobes moving! It’s too easy to get complacent otherwise.
Macro Strobe Positioning
Underwater macro strobe positioning follows the same backscatter and targeted lighting principals of wide-angle shooting, but on a much smaller scale.
The most basic position brings the strobes in close to the housing port and angled slightly out. If looking down over the housing from the top, imagine the strobes angled out at an 11:00 and 1:00 position. This position is a great swim setting for compact, mirrorless and DSLR shooters, as you’ll be ready to shoot anything that comes along at any macro range. The downside is that this position is more prone to backscatter and often results in a flatter image with less shadow and contrast.
The close-focus macro position addresses these issues by pushing the strobes out in front of the housing port and turning them inward towards the port by as much as (+/-)120 degrees. The combination of a close subject and rotated strobes means that only the edge of the cone of light is being used to light the subject while the rest of the light hits the port and/or diopter. As a result, the water above and behind the subject remains unlit, minimizing backscatter. Stronger contrasts and depth are produced from lights on opposite sides of the subject like this.
An important note with this close-focus position is that stability is essential. If we’re trying to dial in strobe beam angle to within 1cm around a subject but the camera is moving back and forth by half a meter, the whole exercise is futile. I stabilize shots by placing my reef stick tip on bare rock or the sand in order to help stabilize the camera while working on macro and supermacro shots.
Translucent subjects will glow when light is shined through them, often referred to as backlighting. There are several styles of backlighting, but the most common can be achieved with the close-focus macro strobe position above. If the subject is small enough, the diffusers on the strobes spread out the light enough to shine through the subject, creating that glow. If you’re looking for more of a glow, try pushing the strobes forward a bit so that there is more light on the back half of the subject.
Other backlighting techniques include off camera lights/torches and camera settings that accommodate for the blend of strobe light and ambient light from the torch, so we’ll skip over those for now.
Single Strobe Lighting
Macro single strobe positioning is just like wide-angle, with the strobe directly over the housing in the 11:00 or 1:00 position. The precise position also depends on the angle of the subject, as you want the light to come from the side of emphasis – usually the face or front of the subject.
Single strobe shooters can also try the close-focus macro position by turning the strobe inward and lighting the subject with the edge of the cone of light. Remember that stability is essential for this technique.
More Underwater Strobe Positions
There are many more strobe positions to which we can assign super cool names, but the underlying theme is to apply the concepts I’ve highlighted above in each new shooting situation. Armed with this knowledge, you’ll be ready to create the best lighting setup for any situation.
If you’re looking for more details, I’ve also put together a 21 minute tutorial on backscatter and underwater strobe positioning that includes animated graphics, sample photos, and strobe position diagrams. This video is like a personal workshop using the same materials I present during workshops. You can purchase and download it to watch any time.