isolate actor using a clean background plate

DreamArchitectDreamArchitect Website User Posts: 595 Enthusiast
I need to be able to isolate an actor from a shot with no green screen used. I will however have a clean matching background plate. I saw in one of the extraction protocol vfx breakdowns than simon was able to do this for an invisibility shot that was not pre planned. What techniques in hitfilm would be use the achieve this?
Thanks

Comments

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,262 Ambassador
    You want to use the Difference Key effect. This effect is designed to extract the "difference" between two layers, i.e. An actor from a clean plate with no greenscreen.
    I haven't messed with that effect myself, but it's controls should be similar to any other keying effect.
  • DreamArchitectDreamArchitect Website User Posts: 595 Enthusiast
    ok triem thanks for that I will check that out
  • SimonKJonesSimonKJones Moderator Website User, HitFilm Beta Tester Posts: 4,450 Enthusiast
    As a note, difference keying is pretty finicky and rarely produces results as good proper greenscreening. Definitely worth a shot, but don't expect it to be magic. :)
  • DreamArchitectDreamArchitect Website User Posts: 595 Enthusiast
    thnaks Simon, I will bear that in mind. I may well green screen it anyway but also try it with a difference key just to try it out.
  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,262 Ambassador
    Oh... Seriously, if you haven't shot the footage yet, greenscreen it. Difference Key is a weapon of second-to-last resort, barely ahead of just manually doing roto.
  • DreamArchitectDreamArchitect Website User Posts: 595 Enthusiast
    well its an exterior shot and I only have green screen cloth material rather than a spring framed thing so setting up a greenscreen in this particular location isn't easy. That said I will do what I can as it sounds like a difference key could be a real pain
  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,262 Ambassador
    You just need a couple people to stand on a box or stool and hold it. Frames and stands make for better keys, but, remember... If your fabric gets a shadow or ripple that's hard to key... Add a second key for the other green.
  • rgbiirgbii Website User Posts: 965 Just Starting Out
    A PVC frame is pretty easy to make, and can be torn down for transport and storage. You can either clamp your green screen to it, or maybe even use some of the adhesive backed velcro.
  • StormyKnightStormyKnight Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 2,726 Ambassador
    A PVC frame is pretty easy to make, and can be torn down for transport and storage. You can either clamp your green screen to it, or maybe even use some of the adhesive backed velcro.

     

    Yup- PVC is cheap and sturdy too. If the green screen has a hem on one end for a pole to go through you can hang it that way also. If outside, you may have to clamp the sides and bottom of the screen down if it's windy.
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