Chromakey Q and A:

Q: I am interested in doing some jewelry photography on a green screen. Would shooting on a green screen even be an idea to be considered when shooting jewelry or would details be lost?

A: If you are shooting photography i.e. still images, I would recommend shooting each pose with a black screen and a white screen. The white screen would be lit to cast a backlight and effectively give you a matte image. Give a clean, even light on the white and keep the jewel in darkness. Then shoot the jewel in the same position with a black background. Black velvet works the best. Don't lite the black and light the surfaces of the jewel. This way you get a "Beauty pass" which you screen over the background with the matte. If this is moving footage on video of motion picture, you can't use the trick above unless you have motion control to do repeat passes. Otherwise if it's a green stone, I would use blue screen. The problem is that if it is shiny, you will get reflections from the screen.

Q: Can you shoot a person in front of the green screen and then add a background later? Thanks! Bailey

A: Bailey, yes, the best situation from an editorial sense would be to shoot foregrounds separate and composite them later. On the original Star Wars, the backgrounds were to be put into the shots of cockpits with front projection. The problem with this was that the visual effects would have to be finished first so they could be inserted into the background when the live action was to be shot. When this didn't happen, they went to blue screen.

Q: When you use a blue/green screen does the image that will replace it have to be there on a computer that you are recording to (or however it works) or is the image put there later.

A: You don't need the image you are going to use to put into the background but it helps to know what it might be and how the foreground you are shooting with eventually fit into the bacground.

Q: Can a different color be used or are blue and green the best/only choices because of the skintone and lighting thing, like could you use magenta or orange, or would that cancel out red and blue or red and yellow.

A: A red/orange screen is available from many dealers but isn't as popular. The best situation, especially if you are using clay or such with bright colors is to use the opposite color for the screen. You don't want to use a red or orange screen with a red or orange foreground object.

Q: Can a green sheet of fabric be used if it is pulled taut or do you need the special fabric you were talking about.

A: The most important issue is that the screen is evenly lit. No wrinkles or drop off. And the color of the screen must have some saturation, not white, black or too pastel.

Q: Is there a special program you need to put the images on the blue/green screen?

A: Basic compositing programs such as Adobe After Effects are good for compositing scenes and have basic keyers. For good keying of the background, you should get a plug in to go along with the Program. A plug in such as Ultimatte's keyer or Primatte for instance. After Effects comes with a built in keyer called Keylight which works well.

Q: Is there a specific shade and tint of green and blue that you can key effectively? Or is it possible for me to make my own green screen just by purchasing a ballpark shade of green or blue paint or fabric and building it myself? I have seen green and blue screens that you can buy on the internet, and being that im 16, i can't afford it at all. Thank you very much. - Sean.

A: Sean, thanks for your email. Blue and green screens are usually broken into 2 categories: video blue and green and digital blue and green. If you are shooting on DV or video, generally you want to stick with green. The "video" and "digital" generally relate to the intensity of the color. Digital green is a more intense green, while video green is less intense. It's best if the color is less intense but not pastel. The most important thing is how even the lighting is on the screen. No drop offs, shadows or inconsistency in the lighting. Also, not under exposed but not too bright as to "clip." You should do some tests and then try to pull a matte with whatever program you are working with.