Red filter only have any benefit in certain situations and they add a bunch of complications to an already complex process. Too shallow and they make the footage too red. Too deep and they remove too much light (remember that the filter removes blue and green but does not add red). If you leave it on in the wrong light situation, you will have some difficult footage to grade. Even if you do get the on-off timing right, the footage either side of the transition is difficult to color match. If you pan up, all the highlights will have a red tinge.
And why bother with that complication when the GH4 has a more viable solution: the 4 WB presets. Fill these up BEFORE you go diving and flip between them, depending on the ambient light color. I wrote an earlier post on how to do this. Just take a WB setting off four pieces of coloured paper in sunlight, save them in the presets and remember which preset is for which lighting condition. Save that with your other favorite settings in a Custom Setting so you can get back to them quickly if you ever decided to play with MWB while diving. I keep it simple: 1. shallow to mid tropical blue water, 2. mid to deep tropical blue water, 3. shallow to mid greenish water and 4. mid to deep greenish water. These get you very close to a good WB that can be tweaked in the edit. And it doesn't rob you of an f-stop or two.
- thetrickster likes this