Backscatter is the arch nemesis in underwater photography. It can turn an otherwise stellar image into a trash can candidate. It’s deceptive too, often very tough to see in the camera’s LCD screen while underwater. So what causes backscatter? How can we minimize backscatter in our photos?
What is Backscatter?
Backscatter is caused by light reflecting off particles in the water column. These particles could be plankton, particulates or sand – really anything that makes the water less clear. The particles don’t always reflect light, however, since it’s the angle of the light that causes the reflection.
It’s also important to separate haze and backscatter into two different categories. Haze caused by the sun backlighting particles in the water. This haze can be avoided by either shooting at a different angle or by trying to block the direct sunlight with something like a diver, kelp, or dive boat. The backscatter we refer to in underwater photography is caused by our strobe or video light.
Tips to Minimize Backscatter
There are three steps to minimize and/or completely eliminate backscatter in our underwater photos.
1. Reduce Distance Between Camera and Subject
Since backscatter is created from particles in the water, we can reduce the amount of water in order to reduce potential backscatter. This conveniently matches up with one of the main tips for underwater photo and video, which is to get close to your subject!
2. Maintain Excellent Buoyancy
Sand is a major contributor to backscatter, so if you or your buddy stir up the sand then it’s only natural for more backscatter to be present in your photos. Ensure that you don’t stir up the bottom. If you’re with a larger dive group that is causing a ruckus, ask your dive master if you can keep a slight distance from the group, preferably up-current.
3. Use Precise Strobe or Light Positioning
This tip is definitely the most challenging, since strobe positioning is a constant and ever-variable exercise. The goal with strobe positioning is to light your subject without lighting any extra water, because that is where the potential for backscatter arises. Different compositions and subjects call for different strobe positions, but this goal always remains the same.
Snoots and Backscatter
Snoots are a great way to reduce backscatter when shooting. Snoots produce a very narrow beam of light used to emphasize a part of a subject, or create a black background around a subject.
Since such a narrow column of water is being illuminated, it’s only possible for a narrow column of backscatter to be created. The other areas of the frame receive no light and will not contain backscatter particles. And when the snoot is angled correctly, it can greatly minimize backscatter within the illuminated water.
Learn more about Underwater Snoots.