Mastering Backlighting in Underwater Macro Photography

Of all the lighting techniques and tricks to master, backlighting is one of the most challenging for me. There are often issues with how the light falls on the subject, and managing its spread can be tricky. However, when I finally dedicated time to learning it properly, backlighting delivered some of my favorite and most striking macro shots. These shots often stand out from the crowd and add real diversity to your portfolio.

This article explores what backlighting is, its primary uses, how to do it effectively, the camera settings needed to master the technique, and the common pitfalls to avoid.

What is Backlighting?

Backlighting refers to positioning a light source behind your subject to illuminate it from the rear. Instead of lighting the front or sides, the light creates a glowing halo, outlines shapes, and enhances the subject’s natural translucence. This technique is particularly effective with marine life that has textured edges, such as a hairy frogfish. It also works well with translucent fish, like the leafy scorpionfish, where the light can penetrate through the body or eyes. Additionally, backlighting can be used to create silhouettes when it’s the only light source in the image.

In underwater photography, backlighting helps isolate the subject from the background, making it stand out against visually busy or cluttered scenes. The resulting images are dynamic and can reveal intricate details of a subject in ways that conventional lighting methods cannot.

Primary Uses of Backlighting

1. Highlighting Translucent Subjects:
   Backlighting is especially effective for showcasing marine life with translucent qualities, such as jellyfish, nudibranchs, and anemones. Light passing through these organisms reveals intricate textures and internal structures.

2. Creating Silhouettes:
   For larger subjects, like sharks or divers, backlighting can create sharp silhouettes against bright backgrounds, such as a sunburst or open water.

3. Adding Depth and Mood:
   Backlighting can enhance the three-dimensionality of an image by introducing shadows and highlights that emphasize texture and shape.

4. Illuminating Texture:
   Backlighting can make textured details, such as hairs and fins, stand out dramatically against the background.

Equipment for Backlighting

There are a few different light sources you can use for backlighting, each with its own benefits and drawbacks:

• Option 1: A Video Light
  Using a high-powered video light can be a good choice, as it’s portable and versatile. It can be used in different colors, and you can see where the light falls before you fire the shutter, ensuring it’s directed exactly where you want.

• Option 2: A Strobe
  By using either a remote strobe or a strobe connected to your main camera, you can position it behind the subject and fire it only when the flash is triggered. This provides a more powerful light than any video light, making it ideal for using the technique in bright sunlight. However, it’s harder to pinpoint exactly where the light will fall.

• Option 3: A Battery-Powered Small Torch
  A slightly newer option is a battery-powered small torch with various filters and snoot attachments. This setup can provide very precise, small lighting and is easy to move around behind the subject. While it’s not as powerful as strobes, it typically offers a range of color options.

How to Backlight Underwater

Backlighting underwater requires careful placement of your strobes or lights, as well as precise adjustments to your camera settings. Here’s a step-by-step guide:

• Position Your Light Source:
  Place your strobe or video light behind the subject, ensuring it’s angled to illuminate the subject without hitting the lens directly. This can be achieved by positioning the light either directly behind the subject and very close or far away, so the light is either hidden by the subject or out of the frame.

• Use a Snoot:
  A snoot narrows the beam of light, allowing you to focus the backlighting precisely on the subject. This prevents light spill and reduces the risk of backscatter. You can also use reduction rings if you're working with slightly larger subjects.

• Control the Background:
  Aim for a dark or contrasting background to maximize the effect of the backlighting. Adjusting the shutter speed will only affect your ambient light when using a strobe. Remember, when using a constant light, the brightness will increase with a slower shutter speed and decrease with a faster shutter speed. With a flash, the shutter speed will have no effect on the backlighting’s brightness.

• Take Test Shots:
  Small adjustments to the strobe angle, power settings, and camera exposure are often necessary to achieve the desired result. Review your shots frequently and fine-tune your setup as needed.

What About the Foreground?

People often forget that all underwater photos are effectively double exposures: one exposure for the artificial light you introduce and another for the ambient light. With backlighting, if we choose to also light the subject, we’re actually adding an additional light source. Now, we’re balancing three light sources: backlighting, subject light, and ambient light, which makes it a triple exposure.

If you choose to light the subject separately, the image will become a silhouette. This is perfectly fine and can be a creative choice. However, it’s often best to add a bit of fill light in the foreground. This helps bring out the eyes and natural colors of the subject. I often use a subtle snoot light for this purpose.

Personally, I prefer not using foreground fill light with more translucent subjects, such as this leafy scorpionfish, where the only light source has been a single red backlight. But ultimately, the choice is yours.

Camera Settings for Backlighting

Achieving the perfect backlighting shot relies on carefully balancing your camera settings. Since the technique involves both your artificial light source and the ambient light in the environment, getting the right exposure is key. Below are the essential settings to consider when capturing backlit subjects:

• Shutter Speed: Use your shutter speed to control the ambient light in your frame. Faster shutter speeds darken the background, which helps isolate your subject and reduce distractions. If you want a black background, start with a shutter speed of 1/250 and gradually slow it down to introduce a blue background.

• Aperture: Your aperture controls how much light enters the lens and affects depth of field. A smaller aperture (e.g., f/13 to f/16) is a good starting point as it gives you a deeper depth of field. Adjust the light source power afterwards to change the visual effect.

• ISO: Keep your ISO as low as possible to minimize noise, particularly in darker backgrounds. An ISO range of 50 to 400 works well for most backlighting scenarios, but adjust based on available light and your camera’s performance.

• Strobe Power: Start with a medium strobe power setting and gradually increase as needed. Overpowering the subject can cause overexposure and harsh lighting, while underpowered strobes may fail to illuminate translucent subjects effectively.

• Backbutton Focus: Modern cameras typically don’t have focus issues unless you're using a video light, as the light spill can interfere with focusing. If you encounter focus problems, switch to backbutton focus and rock the camera in and out to achieve critical focus.

• Shoot in RAW: Always shoot in RAW to retain the maximum amount of data in your images. This format is essential for adjusting exposure, white balance, and other details in post-processing without degrading image quality.

Common Pitfalls and How to Avoid Them

1. Backscatter:
   One of the most common issues with backlighting is backscatter—light illuminating particles in the water between the subject and the camera. To minimize this, ensure your strobe is tightly focused, and use a snoot or diffusers where necessary. Be especially cautious when placing the light source near sand or other substrates, as they can reflect light and exacerbate backscatter.

2. Overexposure:
   Overexposure of your subject or background is a common problem when using backlighting. To avoid this, keep your strobe power low and consistently monitor your histogram to ensure the highlights are not blown out.

3. Poor Subject Isolation:
   If the background is too bright or visually cluttered, the effect of backlighting can be diminished. To achieve better subject isolation, choose subjects with good contrast against their surroundings, and aim for darker or more uniform backgrounds when possible.

4. Lens Flares:
   If the light source is visible to your lens, it can create lens flares or unwanted reflections. Adjust the angle of your strobe or use light-blocking techniques such as snoots and reduction rings to eliminate these distractions.

Conclusion

Backlighting will take some practice and may cause a bit of frustration during the learning process. It’s easy to give up on quickly, but the effort is well worth it. This technique can truly elevate your photos, taking them to a whole new level. The learning curve may seem steep at first, with a lot to manage, but it will soon settle as you become more comfortable controlling the light and where it falls.

As with any new technique, mastering it and adding it to your arsenal is key. The purpose of learning different techniques is to diversify your portfolio, so be sure not to overuse backlighting. Instead, combine it with other techniques for more creative and dynamic results.