Green Screens ?

[Ringmaster]

also, those green screen images that were bought off of ebay... can they be downloaded to a flash drive and put on multiple computers?

 

[Buckster]

also, those green screen images that were bought off of ebay... can they be downloaded to a flash drive and put on multiple computers?

You can do anything with them that you can do with any other JPGs.

 

[GFruge]

The images I received are huge, but of course they're .tiff files. Quality is unbelievable!!!

Don't laugh here, but I paid a pretty good amount for the backdrops that I did get. They made me a bundle deal, but it was still a pretty penny. They come on DVD for the file sizes. Probackdrop

Very high resolution images for greater clarity when printing large photos.
Perfect for prints up to 20" x 30" and larger.
2800 x4200 pixel backgrounds = 11.76 million pixels
Each file is the highest quality tiff format so there won't be any loss of detail.
Each file is over 33 Megabytes in size for the highest possible resolution and best possible photographs.
Backgrounds can be used with any photo editing software that accepts .tif/.tiff files
Mac and PC compatible

 

[anarchyjim]

the foam-backed fabric is great.

Usually you want people at least 6 feet away. You don't really need to have them much further than that, especially if you're not lighting the background. If you're just using two umbrellas, 6' works great.

Umbrellas or softboxes doesn't make a difference. Umbrellas are easier to setup, so if it's portable, I'd say umbrellas. If it's a studio situation, I like softboxes... a bit better light quality, IMO.

Don't light the background if possible. You want the background to be about a 1/2-full stop darker than the foreground subject. Lighting the background separately makes it more likely the background will be overlit and 1) be too bright and 2) be casting green spill into the scene.

If you're doing a lot of greenscreen, get dedicated greenscreen software. I'm biased since we make a photoshop plugin for it, but honestly the time you save will pay for it. If you're doing a couple hundred shots, saving 10 minutes an image is a big deal. If you're just doing a greenscreen shot here and there, PS is capable but it's difficult to get fine detail like flyaway hair. You'll notice most PS tutorials dealing with greenscreen use black or slicked back hair. Much easier to deal with than a blond with a perm.

As for lighting, a white back/hair light will go a long way to dealing with any green spill. But if you've got 6' of distance b/t subject and background, it's not really necessary.

cheers,
Jim Tierney
Digital Anarchy
www.digitalanarchy.com

 

[Ringmaster]

Thank you all. I guess I need to buy lots of stuff and start playing.

 

[inTempus]

I work to evenly light the background of a green screen. I've found it makes it easier to separate the subject from the background in post. But with good editing software this shouldn't be too much of an issue.

A couple of things you need to think about.

1) Generally its better to not use a color such as white on the subject when shooting a green screen. The white will pickup the green on the edges and make it hard to separate in post. But again, good software will help you with this issue.

2) Get your subject away from the green screen as much as possible. This will help cut down on the reflected green light and reduce the amount of bleed over onto your subject.

Here's a sample from a shoot I did a couple of months ago. I had to shoot the subject in white because of the character we were portraying (Constantine).

Here's the original green screen shot:

...and here's the final edit:

I should also add that I use a simple $40 green seamless paper roll (9ft wide) that you can pick up at just about any photography store like Calumet, B&H or Adorama.

 

[Augphoto]

Interesting and relative thread here.

I just purchased a chromakey backdrop and background stands which should be here by the end of the week. While searching for info on the internet I came across a video Chroma Key Studio Set Up HD - Video which gives background lighting info. It states that two lights should be used to evenly light the background. I will be using a one light set up, as this is all I have.

Will one strobe with umbrella (on my subject) be sufficient or do I need more lights? Some here have said 'not' to light the background and this would sure be easier for me. If I must have the background illuminated, would a different type of light work? My only light is an Alien Bee and I can not afford another one, at this time. I could possible afford a Home Depot type work light but, not another strobe. I would never consider mixed light sources ON my subject but, will it work for a backdrop light?

Any help here would greatly be appreciated.

 

[anarchyjim]

I would test it out with one light and see how things go. Two umbrellas is usually the better way to go... two lights on everything. However, since that's not an option, one light may work. At worst, you'll have a bit more work to do in Photoshop. I'd recommend against lighting the background. Especially with a home depot shop light.

There's no 'magic' setup for green screen. Many configurations will work, it'll just depend on what your shooting and how much time you have to deal with problem areas that'll occur because of non-optimal lighting.

cheers,
Jim Tierney
Digital Anarchy

 

[thoughtcryme]

Video apps include a utility called "spill control" to control color bleeding and bloom from the background into the foreground and vice versa.
I've read about before, and often run into statements from experienced folks who say
1)Backlighting the green screen is ideal, but also the most difficult to pull off right.
2)Don't use ONLY a green screen.
This is important because of hair color.
People with light blonde hair usually have what's known as "ash tones"(dull green).
People with dark blonde to medium black hair have what's called "copper tones".
People with very dark black hair have blue tones.

So the color of the comp screen should be chosen based on a subjects hair color/tone.
I'm sure skin tone plays a role too.

Seems logical though.
If the green screen is a similar shade to the ash tones, spill will present a problem.
Not so much with stills though I'd imagine since it's only 1 frame.
Backlighting provides a seperation.
But if you used a strip of low level lights that are well diffused and shielded from view of the camera you'd think it would negate that need.

I've thought about doing myself too.
I kicked around an idea of painting the wall behind it with chrome paint to constrict the light dissipation.
Or get one of those $1 space blankets and hang it behind the green screen.
But white might be a better choice to offer diffusion.
Or a wall length softbox with the green screen hanging above it at an angle so it lights evenly while occluding the foreground elements.

I recently started toying with a 3D package called Cinema4D.
It's incredible because all of the tools in it work according to real world mechanisms that anyone who understands color theory and gamma can make sense of.
When lighting in 3D, all of the lights you create have attributes that you control to do things like exclude any individual or group of objects from illumination by any specific light source.
You can also create a light that gives off no visible light at all but instead casts shadows from a seperate light source.
You can make the lights any kind of light at all, like omni(point light), directional, spot, area.
You can also make a simple object like a hemisphere or rectangle and turn it into any type of light and the illumination takes on the shape of the object.
You control the falloff completely.
It can be modified by a gradient ramp, a layer mask, a color, a translation..anything really.
Falloff can be set simply to inverse square to take on the dynamics of real world light.
Then you can render a photoshop file that splits the whole image into seperate elements.
So you have a layer with only illumination, or only shadows, only highlights, etc..
There's a layer called depth that controls the depth of field.
Cameras mimic real cameras and you have total control over every aspect.
You can render an HDR image, or load an HDR image and the whole scene is lit to mimic it.

I find myself wondering how some of these concepts could translate into a better real world method.
Like a negative light lamp that cancels out illumination of certain intensities.