creating an alpha with difference

Hi,
i've got a an image with a tree -
so i've used the CC to surpress all of the colors except the tree's green.

I wasn't getting good isolation using primatte so i was wondering

can i create a difference matte of some sort dialing out the grey and only leaving the Green leaves?

how would i set the nodes up?
thanks
peter

Hi Peter,

Are you able to post an image of the tree in question? Difference matting might be helpful if you have a shot with and without an object and then you can key out the difference between them. Are you trying to key out the whole tree and replace the background?

Let me know if I'm not understanding your goal correctly.

Steph