Gel Filters to replicate Water Absorption

Hopefully many of you can relate to me, in that I don't get enough time underwater with my camera to fine tune the settings, when I do get to go diving and the conditions are perfect (or near too) I'm having to decide - get some video - or go and fiddle with the camera - I always end up setting the camera to a punchy profile and go recording - so no doubt could do better.

Which got me thinking... Would anyone know of any gels (Tiffen etc) which we could use 'on land' which would replicate water absorption.

That way we could fiddle without getting wet.

Difficult, absorption depends on depth. You can try Lee 201, 200 and 132, or something similar for blue water. Green is a much more complex question. There is some spectral data available, but i think it depends very much on the actual, local conditions. You can try matching these spectra: https://scienceofdoom.files.wordpress.com/2010/10/from-light-absorption-in-sea-water-2-wozniak-2007-499px.png?w=584

I agree that exact matching will be impossible - especially as it dependant on so so many things, water temp, clarity, sun position, clouds etc etc

But we could at least see what is happening with the WB for a simulated depth and with various filters /stacked filters we can see what results are

What are you doing when you fiddle with the camera? I have all the settings saved up in the custom 1, 2 etc. The only thing left is do a custom white balance reading before shooting. The Nauticam housing is ergonomic enough that you should be able to weak aperture, shutter speed and ISO without looking at the housing so you just look at the LCD to make sure the exposure is right and start recording.

Sorry if I was clear

I mean, I haven't really nailed down:

• Which colour profile to use (using Natural at present)
• How much contrast, sharpness, shadows/highlights to adjust
• What the cast options do when manual white balancing
• What the minimum aperture for acceptable corners is (with the 7-14mm)
• What ISO underwater I would be happy to go to
• Is CineD or CineV or VLOG really worth looking at
• What gives you a better WB? Hand, Pointing to sun, Pure White Slate, Grey Slate, a warming (slighty green) Slate

I've got X-Rite colour checkers which I would like to take underwater and get a feel as to how the camera reacts to the loss of the Red channel (as for sure the GH4 isn't great) and from there you could build a present to adjust. Plus now Color Finale does some auto-matching with known color charts.

All this, and yet every time I go diving, I just forgo it all as I'm normally diving a new place, stick the camera on Natural (with increases in sharpness and contrast), ISO800, Av Mode and 23.98fps (and white balance off my hand) - I really feel the camera can do a lot more (as evidenced by the 'topside' users who spend time calibrating their cameras and seem to great incredible results.

So back to my thought of replicating the loss of Red and Orange and staying dry - and being able to reproduce result after result

Most items on your list need the camera to be submerged. BTW corner sharpness may not be an issue if you "don't have" corners! (E.g fish in open space). ISO is the only general thing: you should stick to the values you are fine on land and avoid over/underexposure.

Corner sharpness: in 4k video or stills, you'll want to stay around f/8. Any wider will mush your corners (if there are...).

Loss of red: one has to use filters to cut down the excessive blue-green channels, otherwise red will be multiple stop underexposed.

The only way to learn it is while diving. Just to handle the stuff, practice to quickly adjust settings underwater, a pool/local quarry is perfectly fine, all you need is 2-3 weekends to get a handle on things, that may be faster than a shipment of filters.