Step 1
Firstly, open up the image that you would like to vignett. I have chosen a mountain photo from flickr.
Step 2
Select the elliptical marquee tool from the tool box. Make a selection of the part of the photo that you would like to keep.
Step 3
Next up, we're going to be adding a feather to this layer. We are going to be doing this by going Select > Modify > Feather - use a feather radius of 20px.
Invert the selection (Ctrl + Shift + I).
Step 4
Now we are going to delete everything around the part we want to keep - so hit delete on the keyboard. As you can see, we can see the white and grey boxes in the background (which means it's transparent - we'll be adding a background shortly).
Step 5
Lastly, we are going to be adding a background. Create a new layer (Layer > New > Layer) and fill (Edit > Fill) it with a light blue (or a colour of your choice). Move this new layer below the image layer in the layers window.
This is how it looks with the original background with a lower opacity.
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