I have had several comments about blurring a background in PS or using a Gaussian Blur in PS.
I use PS but not an expert or even a good novice,so any places to go to learn about this process,besides official PS manual.
The independent sharp subject layer above the blurred layer keeps the edges intact, In conclusion you can independently adjust the subject and/or background for exposure, color, filtering, etc. And, adding a layer mask to each layer will provide even greater control.
1.) Isolate the subject on the new layer as precisely as possible with whatever selection technique works best for you.
2.) use Ctrl J placing the SELECTED area/subject onto a transparent bkgd.
3.) Ctrl click the new subject layer thumbnail to re-activate selection, click on the original background layer, and then Ctrl Shift I to invert the selection.
4.) Ctrl J again to place the background w/o subject onto a transparent layer. Note -you want the subject layer w/transparent bkgd to be above the background w/o subject layer in the layers palette.
5.) Apply the blur to background w/o subject layer
6) If necessary go around the boundaries at a very high magnification and modify the edge with a tiny, lowered opacity soft edge eraser.
Suggested technique for blurring background using Photoshop. I don't have a bird handy, so I'm just using a throwaway image to demonstrate.
Step 1. Duplicate the image and mask out the subject. Whatever your masking technique (Quick Mask, Quick Select, channels, etc.), this is where you want to be precise, separating the subject cleanly from the background.
Step 2. With the layer (not the mask) active, go to Filter > Blur > Lens Blur. In the dialog box under "Source," choose "Layer Mask." With preview on, set the blur radius to suit your needs. Click OK.
This seems to be a good technique, but it introduces a lot of noise on the BG. the idea here would be to have an OOF BG but with no noise. Here one could go back to PS and apply some gaussian blur to the BG, but that would be double work.