postproduction-work with green screen

for our post-production brief we had some introduction in greenscreen compositing. we had a well-lit greenscreen set up with 4 red-heads. good lighting is a key element in capturing a good footage for peaceful post editing. two red-heads were pointed at the green background in order to get clear and smooth shot of green layout for further keying. the main key light or also called “hard light” is adjusted so that it shines on person from approx 45 degrees angle. it is important not to direct spotlight straight from front which will make person or object of interest look very flat. there should be some shadows on the face but no shadows on the green background. to make shadow appear more smooth and transparent, we clip some diffuse material on head of the key light. in order to get rid of shadow completely we need to double diffuse layer. to make chromakeying more successful we need to adjust one lamp behind the person. it will enhance the outline shape and make the edge brighter and , respectively, easier to key out. in this case it is important to watch out for lense-flares. here is some simple chromakeying and post-editing done in after effects. just messing about::

this is the root footage i was playing with

i did slick chromakeying with help of a plug-in built for after effects. it is very easy to use and is very effective. a great time saver and shit in teaching properly how to key out problem areas such as shadows. then i brough in some background image and tracked a gorillas head on top of my body. it is not good tracking and needs some manual adjustment in some places. for this sort of experiment i didnt bother. i used my friend’s music mix for sound.

i had an idea how to make my video more twisted and fucked up. i didnt like how it looked and it needed some sort of “strangeness” to it, nothing much , just bit off being blunt and silly. soooo, what i did here is i time stretched previously rendered video. it not only stretched the video flow but also audio and it was just what i was looking for. i did play with some effects and made this image totally reduce into animated noise. my aim was to create just a distorted layer of same video which i intended to blend with the original.

here is the final render with time stretched audio and effect layer which went through, again, some heavy effects till total non-recognition. this is just a mess but it gave me main idea how to chromakey in after effects with just one click of took me not more than an hour to come up with the final render which made me think of how chromakeying today on simple personal computer can be done so easily and quick in comparison to old techniques film people had to hassle through on more vintage and completely! analog machines. bluescreen compositing (“greenscreen” name is slightly less common in film industry) has been invented around 1930s which originally was a very expensive film process involving pricey lithographic colour separation. today it can be done with just one click of a mouse button (surely it depends on how good the footage is). video chromakeying in television industry is referred to as CSO – colour separation overlay. such name was given by BBC team in 1960s. Petro Vlahos who is a bluescreen inventor was awarded a Lifetime Achievement Award by the Academy of Motion Picture Arts as an acknowledgment of how popular his technology had become.


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