Best way to greenscreen images/videos with black as the chroma channel?

brajbraj Website User Posts: 75

I just upgraded to Pro, now I need to upgrade my skills. I have a little tool that I will be using to make backgrounds, but black is my only option for using for transparency for the chroma key. What are my best options for getting the nicest, most detailed and hassle free transparencies, this will include leaves and trees, so lots of small bits that need to be transparent. Thanks in advance! 

Comments

  • OutreLimitsOutreLimits Website User Posts: 37

    I've used Demult successfully for compositing fire. It may work for leaves too. If not, you can also try a Luminance Key, and set it to Key Out Darker than your threshold value.

  • brajbraj Website User Posts: 75

    Yeah, the Luminance Key is what I have had the most luck with so far. 

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,264 Ambassador

    Back lighting your subject so it doesn't fall into dark shadow. 

    Bottom line is Demult and Luminance Key are both contrast-based filters. You have to lift all the shadows on your subject while keeping a clean, dark background. The secret to any key is to shoot it correctly. 

  • brajbraj Website User Posts: 75

    Thanks everyone.

     

  • Jarrahv1Jarrahv1 Website User Posts: 98

    go old school.  this is where knowing how things were done in the past helps.

     

    make a duplicate.

    crank up levels.  blacks in one pass.  whites in the other. 

    what you're looking to do is completely wash out the subject matter and create a traveling matte.  this is where you see a white spot.  once you have this.  you have alpha channels.  black becomes invisible once set to screen.
    you can use a few different programs to do this.  if you have photoshop.  you can use that.  you can do it in gimp.  you can likely do it in hitfilm.  i'd have to try first.  but that's how i'd tackle it

  • Triem23Triem23 Moderator Moderator, Website User, Ambassador, Imerge Beta Tester, HitFilm Beta Tester Posts: 18,264 Ambassador

    @Jarrahv1 gives fantastic advice here (Jarrah, look at the Threshold effect in Hitfilm for a quick way to separate the white matte from the background).

    Jarrah's advice strengthens mine. You must learn how lift the shadows on the subject enough to separate them from the background, and that's all in the lighting. 

  • Jarrahv1Jarrahv1 Website User Posts: 98

    Thanks @Triem23.  I'll give it shot if i get a chance.  just working on physical props for a film shoot atm.  4 weeks is going to go fast so i can't promise.  But I think that's the simplest way to deal with it (as long as it's non compressed footage / image.  then you'll need a blur and that's going to start to get messy)

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