Spooky video using OpenShot's Chroma key and alpha channel

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Spooky video using OpenShot's Chroma key and alpha channel

Postby Bettina Binks » Sun Nov 27, 2016 1:18 pm

Note to self - when using a green chroma key background, dolls that glow luminescent green are perhaps not the best choice for the foreground! On the other hand my animated bats might not be up to the standards of Studio Gibli (not quite) but I was pleased with them. The bats were made in GIMP and animated as if they were going to be rendered as GIF,s but then I captured the preview using "RecordMyDesktop". Although the wing flapping animation was done this way, the bats are moved about the screen using OpenShot's "layout" properties. The mist was also made in GIMP. I made along wavy line that was semitransparent and imported the PNG into OpenShot and used the "layout" to make it move left to right. As the PNG reached the end I dissolved it into the next one and layered it with different speeds of the same video. I then re-imported that video into the main project and made it semitransparent. The dolls of course were not animated - I relied on the dancing ability of Yasmina, Jade, and Sashabella!

https://youtu.be/e3O6kO1OMkU
Bettina Binks
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Re: Spooky video using OpenShot's Chroma key and alpha chan

Postby XXLRay » Sun Dec 11, 2016 9:51 am

Not bad. Chroma keying needs good lighting and can still be hard to master. Try using a different colour like blue as backdrop when you are using greenish dolls ;)
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Re: Spooky video using OpenShot's Chroma key and alpha chan

Postby Bettina Binks » Tue Dec 13, 2016 10:50 am

Thanks Mr XXLRay! Actually, blue was the chroma key colour used in analoge TV, as blue is the colour which human skin tone has the least of - although sometimes the weather girl's ultra blue eyes would have the map Britain visible through them! I think in the digital domain green is more commonly used as the chroma key colour because green has a higher level of luminance, and so has a wider voltage range associated with it. It's always harder to do chroma keying in post. It is much easier to do chroma keying through a vision mixer because if there are any shadows on the chroma key background, or if the lighting on the chroma key background is uneven it is apparent straight away and can be corrected. If you shoot everything and do the chroma key in post then it's a bit too late; you have to make the best of what you have. My main problem with the video above (apart from the dolls glowing green) was that the camera has an auto iris that can't be switched off, so every time the dolls moved to take up a larger or smaller part of the frame the iris changed and the whole picture varied in saturation. I probably could have got better results with a blue background for these particular dolls, but I didn't want to shell out for another tin of emulsion! I would also have got better results with tungsten lighting. Tungsten filaments can't cool down instantly so they give a more constant light, where as LED and Florescent lighting does flash 100 times per second when running off of 50Hz mains, which produced patterning. Must try harder next time!
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