Photoshop remove inner border from selection

Question

I was wondering how could I achieve to have a unique selection from a "border".. Better: How could I switch from a "ring" shaped selection to a "circle" one??

Answer 1

Hold down the Shift key while dragging with any of the Marquee selection tools and you will add to the selection.

For a ring shape, you would hold down shift and with the Elliptical Marquee, draw a selection to cover the inner portion.

Answer 2

The simplest (and easiest to make accurate) way to get a border selection from a selection is to start with the inner circle, then use Select > Modify > Border and enter the width you need, in pixels.

This avoids having to start your second selection marquee exactly in the center of the existing selection. It also works for any shape.