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Advice for KEYING out WATER

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Yves Bourgeois
Advice for KEYING out WATER
on Nov 30, 2011 at 6:53:01 pm

Hey everyone, I'm a long-time browser, first-time poster.

I'm in pre-prod for a shot where I'm looking to key water being splashed, with nothing else in frame, no talent or anything. The footage will be super-slow motion, either by overcranking in-camera, or with Twixtor if I can't get the gear I want.

My question is how to go best go about this to avoid any pitfalls, or nightmares in post. What I've found so far suggests to shoot on black, as green screen will bleed through, and to light from underneath. Any thoughts on this? Anyone with experience? It seems hard to believe that no black would be leftover and the complexity of the water would make rotoscoping almost impossible, and I really don't want to go there anyways...

Any thoughts would be much appreciated.
Thanks,
yb


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Dave LaRonde
Re: Advice for KEYING out WATER
on Nov 30, 2011 at 7:37:10 pm

It's one thing to say, "I want to key water splashing." The real question is "why?"

Once you have this shot -- however you end up getting it -- what's the necessity for keying it in the first place? Why wouldn't placing the subject in the appropriate environment work even better?

Without additional information about the entire shot, it's difficult to give reliable advice.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Yves Bourgeois
Re: Advice for KEYING out WATER
on Nov 30, 2011 at 8:06:54 pm

It's very important for me to able to manipulate the water separately from the background. As I mentioned, the water will be shot at a very fast framerate, or at least slowed down drastically in post, and I want to place it in an environment that is realtime, as well as be able to place it in more than one environment. This is why I want to key it out, being able to isolate and control it separately from the background is imperative for this project.

And just to be clear, I'll be throwing varying amounts of of water in the air, from a few drops to large amounts on different shots.


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Mark Suszko
Re: Advice for KEYING out WATER
on Nov 30, 2011 at 9:39:39 pm

It's been done already...

http://www.digitaljuice.com/products/products.asp?pid=1592

And they have more, including paint throws.


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Mark Suszko
Re: Advice for KEYING out WATER
on Nov 30, 2011 at 9:40:29 pm

You shoot against black and you don't need to key, just change the blending or transfer mode, and it is in your new scene ready to use.


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Dave LaRonde
Re: Advice for KEYING out WATER
on Nov 30, 2011 at 9:42:31 pm

[Yves Bourgeois] "It's very important for me to able to manipulate the water separately from the background."

We have water and a background so far. Is there also a subject in these shots? If so, does the subject get wet? Does the water splash off the subject?




[Yves Bourgeois] "the water will be shot at a very fast framerate, or at least slowed down drastically in post"

"A very fast frame rate" can mean different things to different people. For someone used to editing at 23.976, shooting at 59.94 and conforming to 23.976 might look very slow -- it's 2 1/2 times slower, in fact -- but it night not be slow enough enough for your needs. It's almost impossible to slow down footage drastically in post without image degredation. Frame rate conversion software like Magic Bullet or Twixtor is good, but it can't really work miracles. You may have to rent a camera that can shoot at a fast frame rate to achieve your goal.



[Yves Bourgeois] "This is why I want to key it out, being able to isolate and control it separately from the background is imperative for this project."

Unless this water comes from the Ganges, Amazon, Mississippi, Volga, Nile or a similar source, it's probably clear and colorless, with turbulence and air giving it some gray scale value. Is this the case for you?

I think you should answer many of your own questions by running tests. If you own the camera you have in mind to use, shoot some footage under the conditions you outlined in your first post. See if you can get the look you want. Use a piece of frame rate conversion software to see if it will do the job for you: you can get a tryout version.

You'll only be out a little time by doing so.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Yves Bourgeois
Re: Advice for KEYING out WATER
on Nov 30, 2011 at 10:13:02 pm

Hey thanks guys,

@Mark, that's good to hear re:
You shoot against black and you don't need to key, just change the blending or transfer mode, and it is in your new scene ready to use.

I was expecting to use luma key, but that sounds easier. Have you every tried anything like this? Do think it would come out clean?

@Dave, I did not include that level of detail because I did not think it was relevant. There is no other subject, just a background or environment in the shot, and yes the water is indeed clear.

I did not include the actual framerate either because it not yet determined! If you see my original post, I mention that I would want to do the slow-mo in camera, and if not use Twixtor, but it's still budget depending at this stage. I am also aware of Twixtor's limitations, but it can give very interesting results.

The reason for posting in the first place is to get some technical advice, possibly even from people with experience with this subject matter, for how deal with this in post and how to light accordingly. I will of course do some tests if I can, but again the amount of testing is budget dependent and it might not even be a possibility.

As I mentioned, I am still in pre-production but trying to anticipate problems down the road by seeking advice. I work in post-prod and want to properly plan this shoot so that it flows in every stage of production, instead of trying to just "fix it in post".


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Dave LaRonde
Re: Advice for KEYING out WATER
on Nov 30, 2011 at 10:21:02 pm

in which case.....

I recommend shooting footage to determine the necessary frame rate first. If the camera immediately available won't cut it, that's a major concern. Then use that same footage to play around with blending modes as Mark recommends.

Kill two birds with one stone.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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Yves Bourgeois
Re: Advice for KEYING out WATER
on Nov 30, 2011 at 10:37:14 pm

I'll definitely play around with the blend modes when I have some footage, it's just good to hear that it sounds feasible. At this stage, I am doing preliminary research, and am trying to avoid trowing myself into a project that can't even work technically. If I can come out with a clean picture, and not pull out all hair in process, I'll be happy.

And as for the framerate, that will come in time.


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Erik Eliason
Re: Advice for KEYING out WATER
on Jul 3, 2014 at 5:23:07 pm

Wow Yves, that was a lot of explaining to do for your simple question ;)

I am too in pre-production of the same task, shooting water in slo-mo with green screen. I normally work in post so using Key Light in AE is what I have good experience of.
Will use the Sony fs700 at 240fps and eventually some Twixtor on top of that.

I will color the water red so I imagine it to be easier to pull the key than with just plain water but I'm still curios of your experience and final solutions. Did you get all details of the water highlights and shadows? Did you go with black BG or green screen in the end?
Do you have a link to what you shot?
Any thoughts on illumination design?

Best //Erik


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