Dulling down overlapped blended polygons

Im looking for a method so my additive blended polygons dont go to quick to white(*) ( by additive + dont strictly mean ONE ONE but any blending method that brightens to region )

(*)something like
0.5 -> 0.6 -> 0.68 -> 0.74 etc

But I cant how I can achieve this, perhaps with use of the stencil buffer?

Any ideas?

cheers zed

Try to lower the blending factors. That would be the most simple solution.
There is another solution if you cannot apply the previous one because of image quality loss. Use a floating point frame buffer and use one of the tone mapping techniques to convert the high dynamic range to the [0,1) interval.