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Underwater Green Screen?

Jordan Buck

Jordan Buck

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Hey Everyone,

I am currently planning a shoot and trying to work out some logistics and thought some of you may have been in this situation before so might be able to impart some wisdom.

I have been working with a band for a while and have done a music video for them before, he recently came to after watching science of sleep and then a portis head video with an idea for a video that would require going underwater.

They arent a huge band and were working with a very tight budget (when are music videos not nowadays)

The idea is to have the band members singularly shot underwater and then keyed out and put on other moving footage to create a really surreal like dream sequence.
With the budget and nature of the shoot we are planning to shoot through the tank so there is no need to submerge the camera etc.

We are going to be using a medium sized tank -

image13.png


But my question is - if I put this in front of a green screen, number one would it work? number two how much light would I need realistically for a clean key?

Any wisdom greatly appreciated.

Thanks!
 
green screen always works if you set it up correctly, and it always gets messy if you don't. underwater greenscreen is probably the most challenging, so do your homework and make sure you understand how to get a well-lit screen and use those same concepts underwater. i recommend having someone there that knows what they're doing, and it'll really help to have some realtime (or near realtime) feedback for setting up the shot. each person will have different challenges as far as the setup and the composite. do not under any circumstances underexpose... i'd shoot at around 320 ISO and just like in any situation you want your screen exposed somewhere within 10% of middle gray and very evenly lit. be careful with particles in the water, make sure your glass is clean, watch out for stray reflections and shadows. i highly recommend a test shoot and/or onset quick composites. very helpful to have your backgrounds figured out and generated or at least previsualized beforehand as well. good luck.
 
I was taught one technique - compositing water I asked the shot to be "black screened", basically blackish back/grey ground and a bit over exposed foreground - then just in nuke shifted the brightness down a bit so the foreground didn't look overexposed (which made the grey/black almost pure black) then did a simple add. Anomalies didn't matter as much as you'd think with the add since underwater there are all sorts of light rays and light patches. This technique also allows quick was of creating masks.
 
Thanks for the advice guys, I am going to search for another body to get involved and do some on set tests as you mentioned, and have a day before the shoot to run some tests on, I think its worth doing it all right as I think the results could be really good.
It is becoming apparent, as I thought that this is definitely going to be a challenge.

But hey... who doesn't like a challenge...
 
good idea. patrick is right on as well, especially if you're going to have a dark background in the end. i cannot recommend enough having your background plates ready or at least prevized before shooting any greenscreen ever, especially underwater.
 
Whether its green or blue (as above), its pretty easy to see the amount of spill and reflection you are going to get. The tank is really small and you can't get 10-12' from the background.

Less light and Patrick's black screen idea may be a lot better than more light with green or blue bouncing all over.
 
i would tend to agree with you, but i actually will assume in this small situation that the spill may be severe although pretty well across the board and easily compensated for. the other side of this whole thing is correct compositing. it's very common but absolutely silly to try to do it all with one key (i.e. one effect, node, etc). usually you want to preprocess both the image(s) to be keyed, and a corrected image to apply that matte to. i don't recommend bluescreen underwater, but ymmv.

hdr-x (with something like rsmb) is not out of the question in the case of relying largely on luminance with the blackscreen method, although i've not tried it.
 
I've done chromakey water shots before as well. I'm with Patrick on this one, shoot black-screen. :)

In my experience, green doesn't work worth a crap under water and if you can't manage to black out the background, then go for blue. There have also been instances and example of people using a red screen for underwater, but once again this can harbor some challenges and I would not recommend based on the photos shown, if that's your setup. I worked on a shoot where we attempted a red screen as an experiment and it was a failure.

If you can get the camera in the water and have more separation between your subject and background -- change locations to a bigger pool, whatever, that will really help. That setup in your pictures looks like an impending VFX nightmare.
 
Black screen does only work if the composite background is much darker than your foreground. For example a girl with black swimsuit will absolutely not be possible to additive key onto something that is relativly bright... and just word possible example nothing is additive key able onto white. So no do not go that way if you are not planing to put in a pretty much black background.

Blue screen works. green screen works. Whats the best of the two is depending on what kind of background you plan to put in. If more green in the background use green screen, if more blue then use that.

Most important ( this is usually what fails) make sure the water is clean. Make sure everything that goes into the water is clean. basically you want whats called "gin tonic" clear water no bubbles and very well filtered preferably during a heavy carbon filter.

The screen that you will be using will most likely be ruined due to the clorine / chemicals in the water so make sure it's something that you did not rent and was supposed to hand back in the same shape as you got it. I done under water blue screen stuff in a normal swimming pool and the blue screen did not fade at all but it took some long discussions with the grip guys to convince them that, well if if fades then we buy it. It did not fade, but sure they wanted us to pay for it any way even if we gave their "supposed to be new" blue screen a good wash, it was better after then when we got it. Lol.


might be good to have under water light to get bluscreen light behind the actor. not always possible to light it all from the front window or the top...

Here is a link to the most recent blue screen pool fiesta I did:
http://www.syndicate.se/folksam-scubadogs/

There is supposed to be some behind the scenes shots and stuff there as well.
 
Hey Everyone, really sorry for the radio silence, have been on a job in Austria in the mountains for the past few weeks and had VERY limited access to wifi ( first world struggles )
going to have a proper read through all of these suggestions and tips now and a few of the emails some people have sent me and start working out what we are going to do.

A massive thank you to anyone who has contributed, its really appreciated, its reasons like this I love this site.

Will update soon!
 
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