First underwater videos often look disappointing: everything greenish and flat, without the colours you know from snorkelling. That is not the camera's fault, it is physics. If you understand what happens in the water, a few simple steps will give you much better pictures.
Why colours disappear
Water filters sunlight, and not evenly. Long-wavelength colours such as red are absorbed first, while blue penetrates deepest. Roughly speaking:
| Colour | largely gone from about |
|---|---|
| Red | 4.5 m |
| Orange | 7.5 m |
| Yellow | 10–14 m |
| Green | 21–23 m |
Important: it is not only depth that counts but the whole path of the light, which includes the distance between camera and subject. Even at a metre and a half, a noticeable amount of red is lost. In our often murky lakes, suspended particles also scatter the light further.
White balance: the most important lever
Automatic white balance is often overwhelmed underwater. It is better to set white balance manually at the depth where you are filming, with the camera pointing at the subject. According to retailer information, the Gladius Mini S offers built-in colour correction. Note: from about 18 to 20 metres, many cameras can no longer produce natural colours without artificial light.
Using light properly
Your drone's lamps bring the colours back, but only over short distances. Lamps with a daylight colour temperature of around 5,500 kelvin, like those on the FIFISH V-EVO, only work out to about two metres. Three rules:
- Get close: The shorter the path through the water, the more colour arrives.
- Watch out for suspended particles: If the light shines straight ahead, particles in the water light up like a snow flurry (technical term: backscatter). If possible, angle the lamps outwards or dim them.
- Don't stir things up: Keep the thrusters away from the bottom, or visibility is gone instantly.
Colour correction in editing
What does not work while filming can partly be rescued later, for example with free programs such as DaVinci Resolve, or in Premiere and Final Cut. Strong corrections do, however, produce image noise and visible colour banding. The better your white balance while filming, the less you have to fix later.
In video
This is what well-exposed 4K footage underwater looks like, in QYSEA's official video:
Take a white plastic card with you and attach it to the gripper claw or lay it on the bottom. You can use it to set white balance underwater, and in editing you have a perfect reference for colour correction.
You can find reactions and comments on this article in the Unterwasserpilot forum (in German, English posts welcome).
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