Green Screen practice?

D

DVX100Shooter

Veteran
Is there anyway to practice i.e. fool around with learning how to do various types of Key's without actually shooting against a green screen which I don't have or have access to at this time. When its time for me to shoot against a green/blue screen, are there any plugin's that have cool background effects to add once the green or blue has been removed? Would the Textures in LiveType work?
 
Re: Green Screen practice?

go to a craft stroe, and you can buy a sheet of foam core in darn near chroma blue or green . then youy can mek your own miniature setup to practise lighting , and keying techniques.
 
Re: Green Screen practice?

The foam board is a great idea. I have actually done some small projects using multiple posterboards stapled to my wall. The hardest thing is lighting. If you have shadows, they will be harder to get out. It helps if you can keep the green background further back from the subject. This also allows you to be able to throw the green background out of focus which will make it much more even in lighting and even easier to remove.

But the keys are:
Even lighting with no shadows.
Keep the subject a good distance away from the background to avoid those shadows. (although this does require the background being even larger.

As far as chroma keying in FCP. You can key out any color. Just use the color key and then use the eye dropper to select the color you want it to remove. Then start adjusting settings. Also, keep in mind that you can lay Chroma Key filters on top of each other. So one filter doesn't need to be expected to remove all of that color. so, if you have your green background. Add a filter for that. And then if you have any shadows, you can add a filter to remove the darker green from the shadow.

I hope I didn't confuse you. If you need any more help just message me.

I've also had some experience in a green screen room. Which to say the least is a lot easier.

Some cool effects can be done if you key out the sky in different shots.
Also, don't forget that you don't want your characters to be wearing any color that you will be keying out. So keep that in mind before shooting, and also remind them before they show up.

Have fun!! It's really fun to play around on.
I'll see if i can post on my website a copy of a video i did with three keyed characters. It was just something i did for my friends.
 
Re: Green Screen practice?

you mentioned even lighting when doing green screen shoots. Does it matter what kind of light as in soft light or harsh bright lights or is this more of a light placement issue to make sure that there is not to much light on either one side of the subject/green screen?

thanks for your tips too!
 
Re: Green Screen practice?

Soft lighting is the best because it helps you avoid hot spots of light on the green screen. The goal is to have the green screen lit with the same amount of light evenly across it. So depending on the size of your screen this could take a lot of lighting or maybe 2-3 lights for a small "green screen" made of poster board.

The trick is practice. Go shoot some stuff. While you are recording a test shot, adjust the lighting, while still recording. then when you go to set your keys in. Watch how they interact with how you move your lighting. This will help you out when you come to your next project. The real trick is finding the balance between lighting your subject and also lighting your green screen so that no shadows show. Always light your subject first, so that you can then adjust your green screen lighting to get rid of all possible shadows created by the lighting on your subject.

Go have fun.

Here is a link to a really cheezy video i did for my friend as a gag for his family this last Christmas. We actually just ended up shooting it against my wall which is a green color. It worked alright. I didn't spend much time keying out all the way against his face. I actually completed the video with about 2 hours editing. This is a short excerpt about how i composed it.
http://www.trailingsilence.com/video/compositing-example.mov

Let me know how stuff works out.
 
Re: Green Screen practice?

The key to get even lighting on a green screen is to use an incident meter that reads in footcandles, and spot-check all over the screen to see if you're getting even FC ratings.

(okay, now that John's brain has melted, we'll go with the no-budget way...)

The DVX's "marker" feature is great for this as well. Turn on the "marker", and then take readings all over the screen, and try to make sure that the number that comes back from the marker is the same all over.
 
Re: Green Screen practice?

Barry you opened up a whole new can of worms! LOL! Where do I find the "marker" on the camera? I am not at home now to look it over.
 
Re: Green Screen practice?

Use the Zebra function, when you press zebra you get zebra 1, then zebra 2, then "marker", which is the square outline in the center of the screen.
 
Re: Green Screen practice?

oh! I thought that was what you were talking about! LOL! I thought the marker was just for shot framing? Are you saying that I should turn the marker on then use a light meter to take the readings all over the screen? Okay Im home now, I got the marker on, and everytime I pan the camera the percentage number changes under natural light here in my room. The numbers are jumping around when the camera is not moving as well.
 
Re: Green Screen practice?

ok I whipped out the manual and it stated that marker displays the video level of the image near the center of the screen as a percentage value is what you stated in a earlier post. I just need to know what the percentages actually mean or what is a good percentage to achieve. Does it matter as long as I am getting the same number all over screen or whatever I am shooting when the marker is used?
 
Re: Green Screen practice?

That is a good way to tell if the amount of light is similar. It's not too important what level it is at. It's just a good way to reference and see if the levels are about the same. I think the biggest thing you need to do is just shoot some stuff and bring it in FCP and start messing around with the settings. See what kind of product you are getting and then determine if you need to change how much light you are using.
 
Re: Green Screen practice?

Well, I'll send a couple screen grabs your way if you want to practice on them.

I'm actually practicing chroma keying myself for a short movie I'm going to be shooting in the next month and a half. My results aren't amazing so far, but I'm getting better and I've done this all very cheaply (well, the software's not cheap, nor is the camera, but the greenscreen was.)

Here are a few screen grabs of my most recent attempt at chroma keying. To make the footage easier to key, I cranked the chroma levels up really high. After keying something, it always needs to be color corrected, anyhow:

jon.jpg

jon2.jpg

jon3.jpg


Here are my results using Keylight (part of After Effects 6 pro) and then the Matte Choker plug in. AE6 is excellent for keying, and has built in 3:2 pulldown for 24p and a 24pA mode!:
http://home.comcast.net/~pfhorwitz/jon.mov
The sorenson codec kind of butchers the movie and the cheesy background and mismatched lighting don't help, but you get the idea.

The artifacts around the edges are the trickiest part of keying DV and are impossible to get rid of completely, but they can be reduced. For instance, the greenscreen itself is far too well lit. It should be about two stops darker than the foreground since the difference in luminosity levels help make up for the fact that colors are heavily compressed in digital video.

Here's how I built and set up my greenscreen:
I used two 8X4 pieces of plywood from home depot (20 bucks)
Primed them with some primer: (12 bucks)
Painted them with Rosco chroma key green paint: (40 bucks, and I have lots left)
Lit the scene using one 200w standard bulb to fill the subject, and one 500w halogen worklight (20 bucks) to light the subject's other side. I lit the greenscreen itself with two 300w worklights (20 bucks each). I used foamcore, cardboard, etc. to keep the lights for the greenscreen seperate from those that lit the subject. I also used rosco diffuse gels over the 300w worklights and a couple other bulbs here and there to fill dark spots. I then adjusted the lights' placement based on the zebra lines. I never got it even close to perfect, but the zebra lines were a great guide.

So while better results are possible, it's a lot cheaper than building a real greenscreen, shooting on a less compressed format, or renting out studio space. To shoot, I turn detail DOWN to -3 (I think) because it reduces grain and texture in the painted wood. I turn chroma up to +7 and keep the shutter speed as high as I can without the image getting grainy (to reduce motion blur).

Good luck. You'll find that good software like Keylight helps a lot, as does a lot of experimentation.
 
You must log in or register to reply here.
Back
Top