Grainy effect making image darker :(

[RodeoFawn]

Hi there,
Im trying to make a pattern grainy but every time I use the effect it makes the entire image darker. I need the background to be the same color, just with a grainy texture.... Im not really keen on using the masking option with a texture image because then its just a bunch of white dots... 
Help?

[RodeoFawn]

So I think I figured out that I have to make another shape on top and only grain that and then make that shape more opaic in the transparancy pannel. Let me know if you find another way!