So far I haven't done any color grading or any serious video post processing. I wonder do people use color calibration cards? Sounds like a straightforward way to get colors twisted by the usually non-ideal absorbance conditions.

Something like this:

https://www.amazon.co.uk/DGK-Color-Tools-DKK-Calibration/dp/B00AWT2QCE

Are there underwater-friendly models or shall I keep it in a waterproof pouch?

My question is how you would use this? The cameras that I have used simply have a white balance button, and I simply reference off my white fins if I use it. Are you thinking of taking a shot of the card at the beginning of a clip and then using your post processing software on that clip? Perhaps I misunderstand your question or how you would use such a card, and I apologize if so.

1 hour ago, SwiftFF5 said:

My question is how you would use this? The cameras that I have used simply have a white balance button, and I simply reference off my white fins if I use it. Are you thinking of taking a shot of the card at the beginning of a clip and then using your post processing software on that clip? Perhaps I misunderstand your question or how you would use such a card, and I apologize if so.

Some software, like DaVinci Resolve, has a function where you can set colours using a colour checker, which helps establish accurate colour values.

Here is the process:

https://www.youtube.com/watch?v=mao2HSKxMkY

Underwater, where colours are filtered anyway, it seems a bit overkill to aim for colour accuracy rather than visually pleasing results. For example, the colour grading on BBC Blue Planet is far from technically accurate. That said, some videographers do use colour checkers as a shortcut to establish baseline colour information for grading.

Personally, I use a WhiBal grey card to set white balance underwater, then adjust in post based on personal preference rather than strict accuracy.

Edited 23 hours ago23 hr by bghazzal

I have only seen it working in a studio, which means in perfectly controlled conditions. In the water, color absorption changes a lot with distance, and the orientation towards the sun changes much more than in the air. A good white balance is more than enough. The goal is to have colors that are pleasant rather than faithful

19 hours ago, SwiftFF5 said:

My question is how you would use this? The cameras that I have used simply have a white balance button, and I simply reference off my white fins if I use it. Are you thinking of taking a shot of the card at the beginning of a clip and then using your post processing software on that clip? Perhaps I misunderstand your question or how you would use such a card, and I apologize if so.

It's not (just) for white balance setting although you can indeed set the WB using the grey part. Real-world underwater video LED lights, even the "high end" ones have a far from perfect spectrum that can't just be perfected by a WB setting. Ambient light is also a mixed bag as in real world water absorption is more than just "red-orange-yellow are gradually disappearing". Effectively, the PP software can use the defined color spots of the card to calibrate the entire image. Similarly to white balancing, besides white, other colors are "moved" to their right place, something along this line: https://www.youtube.com/watch?v=PYmhGkVShSI

9 hours ago, Davide DB said:

I have only seen it working in a studio, which means in perfectly controlled conditions. In the water, color absorption changes a lot with distance, and the orientation towards the sun changes much more than in the air. A good white balance is more than enough. The goal is to have colors that are pleasant rather than faithful

That's a valid point. I see Keldan is selling their colorchecker card, but it obviously works only if the card is near the actual target and as you mentioned, angle to the Sun isn't much different either. Cumbersome to arrange in a recreational dive.