GoPro has a Black Friday special on GoPro 9 so I decided to order one to upgrade from my 4 Silver. I'm also curious on the best underwater settings and if I need to use a red filter. I'm going to try using it without the filter and then decide if I should order a Flip filter.
There's three ways to correct the color shift.
1. Bring you own light
2. Filter(s)
3. Correct in post processing
#1 will only work for close up photos within range of your lights, not wreck photos, divers in the distance, etc.
#2 is easy, provided you're not greatly changing depth or switching between using lights and not using lights. Different filters are needed for mid-water, deep-water and lake (green water).
#3 I know it can be done but I'm too lazy or something.
I have a Flip7. Where that really works is where you're changing depths and/or lighting. For example, drop down, take some distance photos of wreck using red filter with lights off (because they can't reach that far anyway), flip out red filter, turn lights on, take some close-ups of fish, oh shark in the distance, lights off, red filter flipped back in, ascend to safety stop to an extremely friendly remora, flip red filter back out since its so shallow and ambient lighting is almost natural, and take some more pics.
Its kind of like a dive computer, if you're doing a square profile then you can use one of the cheap filters that pops on the front, but soon as you start changing things the Flip system is really handy. It's also much easier to use in cold water with gloves than the pop on pop off filters.
I saw big improvements just from upgrading from 5 to 7 in handling movement so I'm sure the 9 will be even better.
I've attached two photos, one with the red filter on, one with red filter off. Same wreck, FW Abrams, Outer Banks, NC.
Sam