How do you produce a perfect Blur background

[hopper8]

Can anyone advise how to blur the background of a portrait when I attempt it I dup the layer make a selection then ctrl J for a new layer then blur the background using gauz blur but I end up with a halo round the selection please help

 

[MsOz]

Contract your selection by one pixel and feather it by 2-3 pixels before inverting the selection and blurring the background. The 'halo' is a sign your selection wasn't precise enough.

 

[Erik]

Madster is right here.

How did you make the selection? Often, it is a good idea to create a mask yourself using channels: choose the one(s) that offer good contrast but no real loss. In case you chose two (sometimes for hair etc you will see that one isn't sufficient), go to Image>Calculate, load both, choose a blending mode and save as a new channel. Work on this untill it's really black and white and then use GaussianBlur a tiny little bit to soften it.
This you can load as a selection.

This often works better than using Extract, paths or the usual selection tools.

 

[Guest]

Interesting to now that Photoshop CS will have a new Lens Blur Filter.