So here at ChiCho we have entered the world of keying green screen. Somewhere in the grape vine I heard that the Primatte RT Keyer was used in the making of “Lord of the Rings” so being a massive ‘nerd’ I got straight onto the Red Giant website (the geniuses who are behind this piece of software) and got into keying some green screen work I had done.
First of all let me say this, as good as the Primatte RT Keyer is, if your green screen is creased or in anyway not good quality prepare to be annoyed! (a problem we came across and have fixed). Second of all please please please uncompress your footage or image so you have a raw file format to work with.
Right so formalities out of the way. How to use it, well I would recommend masking any area of the background that is stagnant first. This is helpful as the keyer then has less to do and your images/videos will be easier to key. The Primatte RT keyer is a bit daunting looking at first what with its abbreviation and functions (BG, FG, Matte increase/decrease, Spill Sponge to name but a few), but after an hour with it or two you will have it down to an art form (which I believe it is and will not be told otherwise).
First of all you need to select the background. From this the background should go black, or near enough as some fine touches with the ‘Clean BG’ tool will soon sort that out. There is a handy drop down menu which will change the image/video from composition to matte, this changes the image/video into greyscale.
The objective is to turn the background all black and the foreground all white (no PhD needed there). Use the Clean BG tool to select any parts of the background that are not all black, I would also recommend zooming in once you think you have all the background black as there is always a few pesky pixels which will cause problems later.
Now for the foreground (the person or object that is the focus of the image/video). Use the ‘Clean FG’ tool to do the same as what you did on the background except turn it white. Simple so far (prepare to be annoyed).
So it all looks good in greyscale change it back it back to comp in the drop down box. Boom! Green spill around the edges of the desired object or person, not the best detail in the hair perhaps. Red Giant have thought about this though and fitted the software with a spill killer function and a spill sponge to get right in and get rid of the green that shouldn’t be there. Their simple to use the spill killer gives you the option of Red, Green, or Blue spill killer just incase you used a different coloured background, and then a strength option to the affect of how much of the spill from the edges you want to get rid of.
Now don’t make the mistake of opting for 100%. If you take it all the way up you lose detail in the edges of the person or object so take it to as far you can without losing detail then use the spill sponge to eliminate the rest by zooming and basically just doing what you did with cleaning the background and foreground selecting the desired area for cleaning up the spill.
So your image/video no longer has spill, and all the background is now keyed out so just the foreground prevails. Well done! BUT wait – you notice the edges are a bit jagged, not all the detail is quite there (I told you to prepare). Well Red Giant has thought about this as well and equipped the software with refinement tools, Matte Minus/Plus, Detail Plus/Minus and Spill Minus/Plus (I switched the minuses and pluses round there, to make it look more interesting and keep you awak…zzzz). These tools are hard to explain to use, using them is trial and error but one or two hours with this software and you will know how to key in minutes (60-120 of them in fact…).
Author: Darren Thomas