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Underwater shooting
Hi everybody,
I am writing to have some suggestions on some underwater footage,
where I will need to replace the background of the pool with a sub-marine landscape.It will be shooted in a swimming pool with a HD camera.
Camera is fixed, which is pretty good for us.We will have an actor moving, the spot is 30 sec long,
so I will personally prefer to avoid to rotoscope for so long.The first idea was to use a greenscreen, but i read also so many people talking about bluescreen;
It will be easier to pull the key of course, but I’m scared it will also remove some other parts of the footage.And at the end I also saw the post here on Crative cow, regarding Chris Cunningham video for Portishead.
“shot in water with only the subject lit so the rest is black. Then it is probably Screen transfered onto the dark BG (Street scene). So there may not be keyeing at all. ”
This sounds very great technique, I am just wondering if it’s possibe in my case, where will be also some set design inside the swimming pool.
Any suggestions will be very appreciated
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2 Replies
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i’ve never tried to key under water footage (that’s my disclaimer)… but i could see that a blue background may have some advantages. one being that you will probably get a blue shift to some degree if you shoot on green, which may be problematic in keying green. the other being you’ll probably be compositing over a bluish underwater scene, so many aspects of compositing a keyed subject over a background, like spill from a blur chroma wall or noise in screen matte, would be easier to handle.
as far as shooting over black and using a blending mode like screen for compositing… when you use screen, it will essentially make black transparent… this would include anything black on the subject, like scuba gear, hair, etc… it may work if your background will be very dark, but otherwise your subject will probably look rather ghost-like.
Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW -
maybe you have a talk to an underwater photographer or filmer before you start shooing right away just considering the background.
in water, fundamentals of physics are changing, may it be gravity facts but be prepared for opto-electronical facts (within your camera) which have to be considered by filming with a camera for every inch you move underwater.
same rules as for working out of water: LIGHT!
a good weight of battery operated scuba-lights would do if the budget does not allow hiring expensive waterproof underwater lights.
daylight that breaks trough the water surface changes with every inch of depth you dive.a good consideration would be using an outoor pool (or indoor) at night, just with the underwater lights on – as long as you can finish your shooting until daybreak.
in the end, ingesting/converting your footage in the highest, lossless format you can achive, is a good way to go.
study some video codecs which could help you having nice results when it comes to key out your footage, repectivelz color correcting you footage, to keep all the details and a sharp crisp image.if i’d work with after effects for the entire shot, i’d probably do a nice rough color correction to the footage to get rid of unwanted color information, precompose it and then keying. its a non destructive process, you alwys can use the matte of your precomp and add it to your original footage if it works better. AE gives you some powerful tools, but consider if you like to try to work in 16 bit or higher (depending on your ingest/image conversion), its a bit of experimenting.
But as i’ve mentioned, try to find the right codec with good chroma sampling and use AE. It comes with color finesse, be shure updating to the latest plugin version, and i’m shure you’ll get some good results.however, good luck mate
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