Intermediate 9 minutes
Lighting: natural light, strobe, video light, and the enemy called backscatter
Where to put the light, how much to use, and why particles ruin so many photos
A beginner photographer points both strobes straight at the subject, the way they would on land, and gets a photo full of floating white dots. It isn't dust on the sensor or an equipment defect: it's the water itself, lit up.
In this article you'll see how each light source behaves underwater (natural, strobe, and continuous video light), why backscatter happens and how to eliminate it, and the five variables you need to adjust on every shot.
Lighting is what separates an underwater photo from a bluish memory, and it's also the part of the technique that's solved more by position than by money. Placing two modest strobes well produces better results than using two expensive ones badly.
The three sources, and what each one is for
Natural light is the only one that can illuminate a large scene. It comes from above, turns blue past a few meters, and its distinct direction makes it work especially well in backlighting, silhouettes, and wide shots with the surface in frame.
Its limit is color, as the article on light underwater explained: past a certain depth there's no red left to recover. Its advantage is that it doesn't produce backscatter, because it isn't positioned next to the lens.
The strobe is the main tool of still photography. It fires a very brief, powerful flash that freezes motion and returns real color to the foreground. Because its duration is so short, it lets you work with high shutter speeds and separate the subject's exposure from the background's.
Continuous light is the video tool and a huge help in macro. It illuminates constantly, which lets you see the result before shooting and makes focusing easier in difficult conditions, but it drains a lot of battery, is less powerful than a strobe, and doesn't freeze motion.
And there's an auxiliary source worth mentioning: the focus light, a narrow, low-intensity beam that helps the camera focus in the dark and switches off the moment you shoot.
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