Green screen issue! Please help!! Oh God please someone help!
by allec isshac
on
Jun 11, 2009 at 7:17:28 am
Hello everyone. i know i posted this question once before a few months back BUT i still cant find a silutioin to this major problem! i filmed with an actor who had blood red hair in front of a green screen. i have about 30 minutes worth of footage i need to key and cant seem to get a good key around his hair. i tried using a switch mate in shake but that didnt work. it just leaves me with green around his hair... instead of the goldish trash around his hair.
a fellow teacher of mind told me that rotoscoping around his hair and then using a paint tool to color the tips would be the only option left for me to do. please say its not so! (but ill do it if i have to)
are there any plug ins out there for shake or after effects that would work for a situation like this? does anyone out there have the answer?! ive been working on solving this problem for about 4 months now and i have yet to make any solid progress...
thank you for your time and i hope that this issue can be fix with your help.
Re: Green screen issue! Please help!! Oh God please someone help! by Aaron Neitz on Jun 12, 2009 at 6:18:25 pm
Do multiple keys, one for his body, one for his hair. It's time consuming, yes.
You need to feed a background image into Primatte so it can gather color data for spill supression. As well as a defocused background.
Then use the spill sponge to get a majority of the yellow out. Then use the fine tuning sliders to gently work those edges.
You'll find his skin colors start reacting poorly, so that's why you need to do a separate key for his hair and then roto that back in.
It's all pretty essential and basic skills you need to learn and practice for keying. I was able to key a pretty decent one in a couple minutes, even from the JPEG.
Re: Green screen issue! Please help!! Oh God please someone help! by Burt Hazard on Jun 22, 2009 at 12:09:40 pm
And I can recommend both THE ENCYCLOPEDIA OF VISUAL EFFECTS and DIGITAL COMPOSITING FOR FILM AND VIDEO books as invaluable for dealing with tricky compositing situations, both available here at the Cow's Amazon store. Steve Wright's book in particular has some great techniques on pulling difficult keys, including stuff like channel shifting and channel clamping in which you are using the Color Correction nodes to pull down the green channel in the foreground actors/objects, etc. in order to get rid of green spill, which can work wonders. (Right now I'm working on footage that has so much green spill that some of it I have to do a full roto job no matter what.)
Re: Green screen issue! Please help!! Oh God please someone help! by Joseph Owens on Jun 23, 2009 at 12:59:58 am
An alternate approach, one that is explored in the Shake tutorials, is to avoid using the greenscreen nodes to do the actual compositing. Instead, use nodes to generate what you will modify into being an alpha channel in a simple Keymix. Once you have pulled a reasonable matte on the greenscreen, pull the hi-con out of the tree, reassign it so that the RGB is occupied by the alpha separation you have just created. It is now eligible for erosion/blurring, multiplication, addition, and so on, with other green mattes that you may have pulled that work better for different areas. Isolate different areas with a roto-shape. Recombine them into a comprehensive alpha, and you'll be surprised with how much control you have over any aspect of the composite.
There is a fairly effective spill suppressor in the nreal Cookbook that can be fairly easily installed if you know how to copy the .nri, .h and UI.h files into the ui folders.
