Keying AF100 footage with different Gammas

PaPa

PaPa

Major Contributor
Hey all,

Just did a couple of quick tests with the AF100 and a few gammas to see how to best achieve a medium/closeup, simple green screen setup with decent lighting.

Here is a link to some samples shot with CineD, CineV, Bpress and HdNorm.

Each zipped folder has 6 shots using different items with various motion blurs, transparencies, hair, etc...

Each shot is around 5 seconds long.

Shot 1: Falling hair
Shot 2: Red ball
Shot 3: Orange ball
Shot 4: Green ball
Shot 5: Clear glass of water
Shot 6: Opaque jug pouring water into glass.

I'm really hoping October Black can take a stab at these and post a vid tutorial. He seems to know his way around After Effects like a champ. I can get a nice clean key, but transparency always gets in the way in the hair and some skin and can't quite grasp the technique he used in his vid tutorial. I kept the corners slightly darker to practice using a crop. Hopefully a few techniques can be implemented here to get the basics down.

CineD shots:
http://www.zshare.net/download/91350701522c8984/

CineV shots:
http://www.zshare.net/download/913507057c907da4/

Bpress shots:
http://www.zshare.net/download/91350892fabdc836/

HdNorm shots:
http://www.zshare.net/download/9135075547c2d5a2/

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Have you shot with your chroma minused out somewhat?

That BG looks over exposed and the entire image looks de saturated from what I can see here.
 
The green is at 50 IRE with a slight falloff on the sides, chroma here was at -3 or -4. BG is definitely not over exposed.
 
You really need the Chroma for the Key.

I always key at 30 to 40 IRE. ( at least 1.5 to 2 stops under the key / "skin tone")

Too dark a green is better than too bright for many reasons.

The frame grab appears also to have a lot of green bounce in the ladies pale skin tone.

Well set up test BTW.

Note : I use the term "over exposed" when I mean that the exposure is above what it should be. Doesnt mean its off the scale or such like. I really should say the level is too high or something else but habits of a lifetime are hard to change.
 
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Thanks. I think this is as good a test as any other really. The keying is working very very well, but the portion that I'm missing is the second step that Black October did in his test here:

http://thedeadwar.com/

I lost a little bit due to transparency in the hair and a little bit in the skin on her neck and forehead. Other than that it's very nice. One click looks decent and all the motion in the hair has absolutely no green behind it, nor does the transparency of the glass or water jug pose any type of problem. Need to nail down those last two steps.
 
Are you talking about the bit where he masks the face? Because I find that simply changing the "Replace method" in Keylight to Hard Light fixes the issue for me.
 
He adds a second layer, expands/grows the screen, makes a second layer with some sort of alpha channel parenting, removes that new layer's grow and... man, it's confusing.
 
Oh, that's easy...you're just setting the track matte on the second layer...make sure in your columns that you've got "Modes" selected, and you'll have a column called "TrkMat". On the second layer set it to "Alpha Matte" and it'll use the matte from the layer above it. Then use Keylight to key out the green fringe caused by the screen grow on the first layer.
 
Looks nice. Something a little strange is happening on her left arm on the brighter side. Some type of darker shade on the other side of the hilight. I'm getting good results in still format, but it's in the motion that it really shows the weaknesses. Especially in the darker regions of the hair and skin. Need to nail down a formula.

I am just starting to learn After effects so even that isn't very simple for me.
 
So all you pros out there, give these a whirl.

I'm having the hardest time with the red ball video. If anyone would care to give it a stab and post your results, that would be great. Files are small to begin with too.
 
Shooter said:
You really need the Chroma for the Key.

I always key at 30 to 40 IRE. ( at least 1.5 to 2 stops under the key / "skin tone")

Too dark a green is better than too bright for many reasons.

The frame grab appears also to have a lot of green bounce in the ladies pale skin tone.

Well set up test BTW.

Note : I use the term "over exposed" when I mean that the exposure is above what it should be. Doesnt mean its off the scale or such like. I really should say the level is too high or something else but habits of a lifetime are hard to change.
Click to expand...

I''m guessing the reason it might be better to expose the green under 50 may be that during the keying, if you replace a value that's darker you're less likely to grab information in skin that's on the brighter side or more reflective?
 

PaPa - gave it a try. Seemed to come out pretty good. What do you think? Sorry about the low quality upload. I got pretty good edge definition without losing any skin tones. There's no real CC on this just a slight S curve.
 
PaPa said:
I''m guessing the reason it might be better to expose the green under 50 may be that during the keying, if you replace a value that's darker you're less likely to grab information in skin that's on the brighter side or more reflective?
Click to expand...



The reason I expose it under 50 IRE ( and well below the key light /skin tone) is you get more chroma and you minimise the green bounce and fringe issues.

BTW: I only use Chroma Green / Chroma Blue BGs when inside the studio. The digital BGs are so bright and so hard to get down to the correct level. They require so much light (= heat) on the subject. The reflectance difference is 2 and 1/3 stops between a Chroma and a digital green BG. Thats a lot of light.
 
Shooter said:
The reason I expose it under 50 IRE ( and well below the key light /skin tone) is you get more chroma and you minimise the green bounce and fringe issues.

BTW: I only use Chroma Green / Chroma Blue BGs when inside the studio. The digital BGs are so bright and so hard to get down to the correct level. They require so much light (= heat) on the subject. The reflectance difference is 2 and 1/3 stops between a Chroma and a digital green BG. Thats a lot of light.
Click to expand...

Fantastic. I will give that a shot and see how that changes my key. These are really tricky beasts.. Mind you even films i see in the theaters with green screen shots aren't always perfect. I can see the glowing and softening around the edges and that's generally from big budget. I wonder what the limitations of the camera are for motion and clean keys.

I'm sure there is also something to be done with shutter speed when green screen and motion come together. This is another domain completely and I can see spending years learning.
 
Dont over train it PaPa. Your test set up was really good and guys are pulling excellent keys off it.

I am only suggesting a couple of tips, to make it easier on the post side, that I have learnt from a lifetime of shooting keys. Most of it on film where you dont have a wfm to work with. The spotmeter and the incident meter were the tools required then.
 
Your tips are great, because i know the better image you get in camera the easier it will be for you in post. It's the post production that I really need to spend time learning as there are just soo many knobs and tweaks and It's so difficult to tell what is needed and where. I'm toying around but keep getting results that are 90% where i want them to be. If i get too aggressive, some hair disappears, if im not aggressive enough, the motion blur has too much green. Such a difficult balancing act.
 
Hey PaPa- I've been doing some keying tests too.
Curious about your lighting- is that two 5600k softboxes, acting both as green screen light and keylights?
I see the reflector under the camera, which i guess is picking up the hairlight?
 
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