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 5 minutes ago5 min by bghazzal