So I was trying to make my own alpha brushes. but I have a problem with the opacity at the edges of the brush... Not being so familiar with blender nodes i'm really not sure how to adjust the settings to achieve a smooth transition outwards.
I think likely its either my camera settings or the adjustments to the image... I'm still trying to adjust the settings and keep tweaking it... but hopefully someone has some ideas what might be causing the problem.
rendered image also has a slight gradient visible below ... ill try playing with the distance... maybe that will help.?