a question about GIMP

[Toho]

hey guys im trying to something and it is taking so long and i keep asking myself that "there must be some kind of tool for this..." anyways i have this area i am trying to color with a transparent color that becomes more stronger the closer it gets to the edge. so i selected the black area so that all additions are inside the circle and slowly use the brush tool to color the border but the problem is i am only human and some parts look diffrent from the rest what do i do? i cant use the blur tool because what im doing would be ruined if i did.
anyways this is what im talking about:


how can i make a smoother version of this? with varying levels of intensity and etc so i can better control the result?

thanks folks
btw i did google this but only got this: which is kind of useless...
http://www.gimp.org/tutorials/Borders_On_Selections/

[Troodi]

Don't know Gimp, but in Photoshop you'd create a red circle, then create a layer mask which has a reduced version of the circle and then "feathered" a specific amount (depending on the resolution would determine the best size, have to experiment to find the level needed). The mask is then "cut" out of the red circle (in Photoshop it's to make the mask black - it's not a color, it becomes a negative space). Because of the feathering, you get a smooth transition of the red color to the edge of the circle.

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---------- Post added 2011-10-21 at 11:10 PM ----------

Gimp tutorial that might help:

http://www.gimp.org/tutorials/Quickmask/

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