Feathering

[rich2005]

(04-26-2018, 11:53 AM)gimp-artist Wrote: I selected an area with the rectangular selection tool. Then I checked the "feather edges" check box in the tool options. Adjusting the radius doesn't work.

The value used is whatever is initially specified. Change the feather value, then drag a selection handle for the new value to take effect.
If you need the specific selected area, use Image -> Guides -> New Guides from selection first

Edit: If you ever use the free select tool - no handles. In that case, after changing the value just toggle feather off then on for the new value to take effect. Maybe not. It is a good question. I have always just drawn in a new selection. I will keep on looking