Adding feathered blur

[Adooby-doobie]

Hello everyone

I want to add a feathered blur to the sides of the image. I used a marquee selection tool and filled it with Gaussian blur. But the edges look sharp. How do I feather it? I added a mask and under the properties panel increased the feather but it doesn't seem to work.

Please help
Thanks 

 

[c.pfaffenbichler]

Seelct the Filter Mask and apply the Feather. 

But maybe you should try Field Blur instead of Gaussian Blur.