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Keying green screen as good as AVATAR??

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Mark Linthicum
Keying green screen as good as AVATAR??
on Dec 31, 2009 at 3:04:12 am

After trying to get a good key from a 4K image I figured i had to settle for loosing hair detail against the green screen, but then I saw AVATAR and the lab scenes the hair detail was incredible!! one strand of hair up against a computer generated 3D object!! how do they do that??

I am using Keylight In AE CS4. I have a well lit green screen, RED 4K image, Brunette Hair, should be a piece of cake!!

Thanks for any info.

I will post an image if i can.

Mark


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Jon Geddes
Re: Keying green screen as good as AVATAR??
on Dec 31, 2009 at 7:06:37 am

I'm not sure what they are using in Avatar, but I've heard from many people that Primatte is a much better keyer than Keylight.

Jon Geddes
http://www.precomposed.com


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Michael Szalapski
Re: Keying green screen as good as AVATAR??
on Dec 31, 2009 at 7:12:28 am

A key depends on a lot of things to look good. The number one thing is good lighting.
Also, Keylight isn't terribly intuitive. Read through as much documentation on it as you can. It can pull great keys even on smoke and windows if you've got good lighting and a good camera (you've got a RED? Jealous!)

To be fair, Avatar had a huge team of people who worked on the post production for quite a long time. It was probably one person's job for a month to get that one hair to look right. So yeah; it's unlikely you'll get that level of amazing with a small team of people under a deadline (or, like I've often done, by yourself with an impossible deadline.)

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.


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Dave LaRonde
Re: Keying green screen as good as AVATAR??
on Dec 31, 2009 at 4:51:13 pm

Michael's right when he says Keylight isn't very intuitive. If you haven't done it yet, you really do need to use the Keylight manual and tutorials. You'll find them on The Foundry web site.

There's also at least one Keylight tutorial here on the COW. Possibly more.

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


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Mark Linthicum
Re: Keying green screen as good as AVATAR??
on Dec 31, 2009 at 7:56:33 pm

Thanks all!

i thought I new Keylight but I might be missing something!

Mark

Thanks, Mark


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Mark Linthicum
Re: Keying green screen as good as AVATAR??
on Jan 1, 2010 at 1:18:44 am

I do not see any tutorials on there site!

i see a demo that seems to have more control than the plugin I have that comes with AE??

I wonder if I need to upgrade?

mark


Thanks, Mark


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Mark Linthicum
Re: Keying green screen as good as AVATAR??
on Jan 1, 2010 at 1:24:00 am

I just found the Tutorials in small print, cant read!

Thanks, mark

Thanks, Mark


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Dean Sensui
Re: Keying green screen as good as AVATAR??
on Jan 1, 2010 at 8:58:22 am

I use Primatte. Here's an example of a typical key.

http://hawaiigoesfishing.com/greenscreen_demo.html

This was a single key. With more time a separate key can be done for the hair and even more detail retained.

Here's another example, also done with Primatte. Note the hair detail retained.

http://hawaiigoesfishing.com/ap_vfx.html

Dean Sensui -- Hawaii Goes Fishing


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Mark Linthicum
Re: Keying green screen as good as AVATAR??
on Jan 1, 2010 at 7:23:18 pm

Nice!

Have you ever tried Keylight? I wonder if Primatte is the secret or with enough tweaking can Keylight do as good?

Mark


Thanks, Mark


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Dean Sensui
Re: Keying green screen as good as AVATAR??
on Jan 1, 2010 at 9:01:36 pm

[Mark Linthicum] "Have you ever tried Keylight? I wonder if Primatte is the secret or with enough tweaking can Keylight do as good?"

I use Keylight in the studio to check lighting and composition during the setup process, but I don't use it for the actual key.

Keylight doesn't have the controls that Primatte has to select green and non-green areas. Primatte's procedure is more than just a single click: you tell it "this is green, this isn't green" by clicking or selecting several areas in the composition. It's so discerning that I've actually keyed green clothing, as long as the green is different from the green screen.

It also has separate spill controls, choke and edge controls, and a set of controls to handle detail.

It'll key veils, smoke, translucent plastics, flame. And "lightwrap" will incorporate the background into the overlapping edges of the foreground elements. This is an important feature that helps blend things together for a cleaner key.

I also use Composite Wizard, which has better lightwrap capabilities, as well as edge blurring and other features.

Dean Sensui -- Hawaii Goes Fishing


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Mark Linthicum
Re: Keying green screen as good as AVATAR??
on Jan 2, 2010 at 12:19:06 am

Downloading the DEMO now!

Thanks!


Thanks, Mark


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Tim Kolb
Re: Keying green screen as good as AVATAR??
on Jan 2, 2010 at 8:38:09 pm

The biggest piece of the puzzle that most seem to miss is that very few keys at that budget level are pulled with one pass and one set of settings.

Often you'll have one person who is being keyed and you'll need one layer garbage matted to isolate the head, and you deal with the hair...maybe another layer needs to isolate a fast moving (blurring) arm or leg...then a chair or a weapon may have some reflective surfaces that need attention, causing some more layers to be generated to isolate those aspects of the shot.

There just aren't that many challenging keys that are done with a one touch/full shot pass.

Keylight definitely isn't excessively intuitive, but it can carry the load.



TimK,
Director, Consultant
Kolb Productions,


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Mark Linthicum
Re: Keying green screen as good as AVATAR??
on Jan 3, 2010 at 8:00:08 am

Hey Tim,

That is 100% correct, and I am not just separating the hair but right and left hair, I cant get keylight to leave the detail not even close, maybe it is that the RED footage is to compressed.

I have attached photos, you can see the right side of the head the clump of hair is missing.




Thanks, Mark


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Dean Sensui
Re: Keying green screen as good as AVATAR??
on Jan 3, 2010 at 12:08:58 pm

Mark...

Your green screen is over exposed and off-balanced.

The RGB values are:
R 187
G 213
B 106

They should be:
R 70
G 158
B 70

If you checked exposure with zebras they should be right at 50%. And you must white balance for the light hitting the background unless you're lighting your background with green light -- and that shouldn't be necessary.

Here's a sample of your JPG composited with Primatte. Keep in mind that this isn't a carefully composited image, and that the green screen is less than optimum.



Dean Sensui -- Hawaii Goes Fishing


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Mark Linthicum
Re: Keying green screen as good as AVATAR??
on Jan 3, 2010 at 8:45:48 pm

Wow! That already looks better from a lower res JPG!!! Primatte looks like it is much better in this situation!

We shot with the RED so it is RAW footage, no looks. I thought Green Screen should be at 70 IRE and that is what we lit the screen at! I will try to stop it down and try to key it again.

Thanks, Mark

[Dean Sensui] "Your green screen is over exposed and off-balanced.

The RGB values are:
R 187
G 213
B 106

They should be:
R 70
G 158
B 70

If you checked exposure with zebras they should be right at 50%. And you must white balance for the light hitting the background unless you're lighting your background with green light -- and that shouldn't be necessary.

Here's a sample of your JPG composited with Primatte. Keep in mind that this isn't a carefully composited image, and that the green screen is less than optimum. "




Thanks, Mark


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Mark Linthicum
Re: Keying green screen as good as AVATAR??
on Jan 4, 2010 at 1:39:54 am

I went back to the RAW file loaded that into AE (AE now handles Raw RED files!) and changed to REC709 color space and the numbers lined up much better to what you suggested, this now keys much better!

The Power of RAW Footage I love it!

Tanks for the help!!

mark




Thanks, Mark


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Dean Sensui
Re: Keying green screen as good as AVATAR??
on Jan 5, 2010 at 2:56:26 am

That looks like a much better green.

After you got your key, you can start making color corrections.

Dean Sensui -- Hawaii Goes Fishing


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Dean Sensui
Re: Keying green screen as good as AVATAR??
on Jan 3, 2010 at 12:26:48 pm

Mark...

Something else to be aware of: Whatever camera you're using has to record the image with normal hue and saturation values. Do NOT use any "looks" in-camera that will affect saturation levels. Always leave that to post.

The reason is that the computer software depends entirely upon chroma information to determine what's foreground and what's background. While it's possible to extract a good matte from badly shot green screen footage, it's not easy. Not even with the best software in skilled hands. And even then rotoscoping might be required and that can be a whole huge headache in itself.

Without top quality chroma information, you will have a very hard time extracting a top-quality matte.

Do the very best you can to get the green screen or blue screen to be properly saturated and accurately exposed. Every shortcut taken in-camera will mean about 10 times more hours spent in post to fix any shortcomings. Conversely, 15 minutes spent to get it right can mean five hours less time wasted making it work.

When done well green screen can be a kick in the pants. When done wrong it can be a kick -- well, in the front of the pants. :-)

The examples I posted, particularly the one for Aloha Petroleum, was a single key. It even retained the fine hairs off Cindy's head. It was shot with a Sony EX1 using the XDCam EX 4:2:0 codec. So it's not the RED codec being too compressed. Also note that Cindy's sweater is actually slightly green, yet it still keyed cleanly.

Hope this helps!

Dean Sensui -- Hawaii Goes Fishing


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Michael Szalapski
Re: Keying green screen as good as AVATAR??
on Jan 3, 2010 at 8:17:28 pm

Back in your original post you said "I have a well lit green screen..."
Sorry. No you don't. I see Dean's already explained it very well, so I won't go into it too, but bud...you need a green screen that's actually green.

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.


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Mark Linthicum
Re: Keying green screen as good as AVATAR??
on Jan 3, 2010 at 8:51:42 pm

[Michael Szalapski] "Back in your original post you said "I have a well lit green screen..."
Sorry. No you don't. I see Dean's already explained it very well, so I won't go into it too, but bud...you need a green screen that's actually green.

- The Great Szalam
"


Michael,

Yes sorry, we did have an issue now that i think about it! I have been working with this footage so long forgot what green looks like!

This is an issue with the RED that sometimes happens, Something to do with 900nm light wave i think. with RED footage you can use different Color and Gamma Spaces when rendering from the Raw footage. i did experiments and this was the combination that keyed the best for most shots even though it is yellowish. i will try again changing the color space.

Thanks, Mark

Thanks, Mark


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Dean Sensui
Re: Keying green screen as good as AVATAR??
on Jan 4, 2010 at 12:21:26 am

Mark...

Regarding exposure levels of green screen, the "hotter" the green screen the higher the risk of green spill and flare. Fine detail and edges get eaten up by the bright background -- exactly what happens when you shoot against a backlight.

Considering that most skin tones fall into the 45 - 65 IRE range (not including highlights), you want to have that background closer to the brightness of the foreground elements, rather than have it overpower them. That allows you to retain finer detail.

With a lower exposure level there's more saturation, up to a certain point. Too low and you start to get closer to the noise floor.

And then there are those situations in which the person is actually standing in a green screen set, and at that point the green will be at whatever exposure works for the subject. You'll have to make a choice of exposure levels to get optimum results.

BTW, Primatte can key just about any color background. The most important is to have a background that is as unique and consistent as possible. What makes Primatte so powerful is that you tell it what "is" and "is not" the key color. It then uses a three-dimensional color space to determine what to include and exclude. And there are a lot of fine-tuning tools that help further define that color space.

Whatever background color you have, it's best to have one that shares as little in common as possible with your foreground elements.

Dean Sensui -- Hawaii Goes Fishing


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Mark Linthicum
Re: Keying green screen as good as AVATAR??
on Jan 4, 2010 at 5:12:03 am

I went back to the RAW file loaded that into AE (AE now handles Raw RED files!) and changed to REC709 color space and the numbers lined up much better to what you suggested, this now keys much better!

The Power of RAW Footage I love it!

Tanks for the help!!

mark




Thanks, Mark


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