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Well, its not my area and i am a little bit scrappy with this. So we have this little device , that we want to show how a real human hand stick to some different places .(for example door,window,gate ,etc) Because we cant go physically over 50 locations, i was thinking about this

I will picture one video, where a hand stick the device to some flat green/blue area, then replace that area with a different picture(s) .

1.Is it possible to make this look real (so a normal eye cant tell)?

  1. Is there any better colour to use on the background ?

3.What is the simplest software that do that on a mac? Can iMovie do that ?

Thank you.

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  • Making green screen / chromakey look 100% realistic takes a lot of time and artistry, mainly because of the shadow the hand SHOULD cast on the surface it's touching. (I left comments about this on Michael Tiemann's good answer below.) To get the most realistic effect, it might be worth your time to go to the 50+ locations and shoot. I have gotten excellent video quality just shooting with my phone. That would definitely limit the equipment you would have to bring to the location!
    – BrettFromLA
    Commented Dec 23, 2015 at 19:01

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The effect you are looking for is Chroma Key, and it is supported by iMovie (according to this Apple documentation). The color green is typically used (and the technique known as Green Screen) because green is not the color of human skin, and thus easy to distinguish. When green is a color that must be used in the scene (for example, if your subject is Kermit the Frog), then Blue Screen is used (and the technique is known as Blue Screen). Sometimes no color works, in which case, people use bright white or dark black. Chroma key software can work for those, too, but technically it's a Luma Key in that case.

As for making it look real--that's a skill. But now that you know the name of the technique, you can find articles that explain how best to do it, and the pitfalls to avoid.

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  • Michael Tiemann gave an excellent answer about Chroma Key. One thing that will definitely help "sell" the effect is adding a shadow of the hand on the "surface". The shadow will have to move with the hand, and will probably be hazy or unnoticeable until the hand gets closer to the surface.
    – BrettFromLA
    Commented Dec 23, 2015 at 18:57
  • In addition to the shadow, the light on the hand has to exactly match the light on the surface. That includes the angle of the light, the color temperature of the light (more warm, more cool...), and the sharpness of the light source (a single lightbulb? Light bouncing off a white wall?).
    – BrettFromLA
    Commented Dec 23, 2015 at 19:00
  • Technically luma keying uses three channels, not two. There is the background channel, the foreground channel, and the alpha channel, which is uses black and white to define the image outlines, and grey scale to define transparency/
    – pojo-guy
    Commented Nov 13, 2017 at 20:30

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