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Old September 25th, 2003, 04:54 PM   #1
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Green Screening

I was hoping someone could help me out with a couple questions that I have. I am fairly new to green screening and I havenít turned out anything good yet. Usually my subject is too faint, not good color, jagged edge and stuff like that. I light the background evenly and I have some overhead lighting for the subject but it doesnít seem to turn out too good. I use halogen court lights for the background and I try to keep the intensity off so it doesnít get too bright. I have not tried it yet, but I just bought the new sony vx2000 hoping that I would help with clarity. I use adobe after effects for the keying. If there is anything that you could suggest that would be great. Also, I am not sure about the setting of white balance on the camera, does anyone know what it should be set at? If anyone can give me any type of feedback that would be great. Like I said I am pretty new to this and I would like to be able to turn out a clear good subject after keying the color. Thanks.
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Old September 25th, 2003, 06:44 PM   #2
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I don't much like the keyer in After Effects. I much prefer the Canopus products for that. This is because the Canopus converters the image to 4:2:2 so their keyer works better right out of the box.

Otherwise, AE has enough tools to do it OK. But they are somewhat tedious from what I can see.

Is your subject far enough away from the screen so that you are not getting green spill on the edges? If you are and cannot move the subject further away, you may need to light the subject edges with a little bit of orange light.

The VX-2000 probably won't make much difference unless your present camera is really bad.

White balance for the light falling on your subject.
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Old September 26th, 2003, 09:08 AM   #3
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Thats for you help

I just have one more question. I am having a problem with the video once I bring it in, it is clear but the hands when they move fast look like the pixels don't match up and become jaggy. What would be the reason for this? Shutter speed and if so what should it be set at to clear that up.

Thanks Matt
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Old September 26th, 2003, 11:10 AM   #4
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You probably have the wrong field order set in After Effects.

When you add a project to the Render Queue, you go into Render Settings and change Field Render to the correct setting for your avi files. The order is normally determined by your editing software.

In After Effects, the choices are Upper Field First or Lower Field First. Other programs may call these fields Odd and Even or First and Second. I'm certain there are other terms as well.
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Old September 28th, 2003, 04:53 AM   #5
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Thing is, to pull a nice key you should both have a hard and a soft key and mix the two. Using a matte control for the blending, you can tweak how large the softer outer edge is (depends on your subject and motion blur amongst other things)

Maybe use a grain killer in your flow too?

Another golden tip is to upsample your dv footage from 4:1:1 to 4:4:4 - the proper way. That way you have much cleaner edges. In short, you should use something like Digital Fusion for that. It's addictive and that's what we use at work.

And blur your new backgroud with your key's matte prior to merging both. Oh, Pull an edge mask and work from that so you can fake radiosity on your final comp...
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Old September 28th, 2003, 09:22 AM   #6
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Ok Great

Thanks I will try all of that. I appreciate everyones help, it worked out alittle better this last time. The only problem I am having is with the green around the feet. It is like a lil green shadow. But thank you everyone for all your help if you have any suggestions on the green around the feet that would be cool.
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Old September 29th, 2003, 07:40 AM   #7
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I was under the impression that if you specified 16-bit color in the project settings in After Effects this would be equivalent to working in 4:2:2, is this correct?
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Old September 29th, 2003, 07:53 AM   #8
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Here is a copy of something I post on greenscreening in Premiere a little while ago. Hope this helps:

-------------------------------------------
I've done quite a bit of green-screening lately, and this procedure will work with any video editing app that has layers (I use Adobe Premiere 6.5, but I don't see why this technique wouldn't work with any editing app). This info applies specifically for Adobe Premiere 6.5, however.

Lets face it: Premiere's chroma-keying is terrible, but I've found a way to get very professional looking composits using only Premiere with no additional plugins or other software:

1. Shoot your green-screen footage. It's good to have a well lit green-screen, but even lighting is more important then brightness (You'll see why in a minute).

2. Capture your footage. Once you bring it into your editing app, load your footage on the first overlay track (layer 2 for Premiere)

3. Apply the filters to adjust the saturation levels of this video clip to 200% or better, especially for the green. This will really bring out the green background. Sorry, can't remeber the exact name of the filter, I'm not in front of Premiere right now, I'm doing this from memory...

4. In the transparency settings, choose Chroma-Key from the drop down and use the eye-dropper to sample the green background, then choose "Mask Only" on the right side of the dialog. Close the Transparency window.

5. Sometimes, you will have to clean up parts of this mask, so if you need to do this, simply create a title and apply white or black shapes to the imperfections to get rid of any trouble spots. You may have to keyframe some of these things so you might have to create multiple titles, it just dends on how "clean" your green screen footage is.

5a. At this point, you can either create a virtual clip or render out this video into another clip. I usually just render this out because my wife says I can't feed both my video jones AND my computer jones (I have a slow PC). We'll be using this clip to create a "cookie-cutter" for our composited final video

6. Make a new project, load your clips, including the mask you just created, and put your plate footage (thats the background footage on which you will lay everything) on the first track (1a for Premiere)

7. Put the mask you just created on track 2 and change the transparency settings for this clip to "track matte".

8. Place your original greenscreen clip On track 3. Change the Hue so the clip is relatively close to the same color as your plate footage. This goes a long way towards eliminating a white or black line around your composited image. You can also play around with the opacity settings. Change the transparency to track matte.

9. Put your original greenscreen clip on track 4, and change the opacity of this clip to around 70%. You may have to adjust the saturation to add a little color back into to image. Again, change the transparency to track matte.

10. Render your image (go get a beer and come back later).
--------------------------------------------------
Sounds like a lot of work, but the results are worth it. No more fuzzy edges. No more green or blue tinted composits. Crisp, clear images. Who needs Ultimatte!

Sorry for such a long post, but this is the exact procedure I use, and I get better results this way then when I use AE.

Cheers,
slakrboy
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Old October 6th, 2003, 09:49 AM   #9
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Thanks!

Thanks everyone again for your inputs. I finally got a good key, but the only problem is. After effects says I don't have enough memory to export. I have been trying to figure it out for a couple days and it is driving me out of my mind. There is no way it can be out of memory. The clip I am exporting is a 21 second clip, with two seperate clips and a background. My computer is pretty robust so that is why I don't think it can be out of memory. I have a dual 3.06 ghz xeon processors and 1 gb of ram. I have over 200 gb on my system probably about 150 gb free. No clue why this would be saying that. Is there a way to allocate more memory with windows to After Effects? Any help will be appreciated. Thanks
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Old October 6th, 2003, 11:11 AM   #10
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I've never had that problem but I think you may be out of scratch drive space? Where is your's set? You set that up under Preferences.
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Old October 6th, 2003, 12:15 PM   #11
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Hi Matt,

You should goto www.dvgarage.com and look at their dvmatte plug-in for After Effects. It works amazing for minidv footage and the keying process is easier. I have used it on crappy greenscreen and it pulled a great matte.


Rob
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Old October 6th, 2003, 01:52 PM   #12
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Size

I looked under the preferences settings in after effects and I saw cache so I went to that and changed image cache to 999% and same with maxium memory usage 999% that gives me 2027mb. I tried to export the quicktime then and it said that

After Effects: Not enough memory to create
2097152kb requested and 2014020kb available.


Quicktime Proccess failed.

It seems like can export the quicktime without audio but once I check the box for the audio to output too it gives me that error.

No idea where to go with this. Any ideas?

Thanks,
Matt
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Old October 6th, 2003, 02:46 PM   #13
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Another alternative would be to look at UltraKey by seriousmagic (http://www.seriousmagic.com)

It makes keying extremely easy and comes with a lot of virtual sets. Plus you won't find a better support staff anywhere.
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Old October 7th, 2003, 12:19 AM   #14
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I think you need to talk to the AE experts on COW or on the Adobe-sponsored forums
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Old February 9th, 2004, 12:21 PM   #15
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Where can I purchase a green screen. I hardly know anything about green/blue/red screens but I would like to learn them so I can apply them to a new rollerblading film I'm working on. Also, how expensive are they?
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