A feathered brush produces an edge that goes from solid "paint" out to less.
Feathering is measured as a percentage.
The hardness of a brush is the percentage of feathering.
A brush with a hardness of 0% has the most feathering.
A brush with a hardness of 100% has no feathering.
You can change the hardness in options bar/Tool Options.
Hardness can also be changed by increments of 25% on the keyboard.
Shift + [ = Decrease by 25%
Shift + ] = Increase by 25%
The advantage of the latter method is that you can see the brush cursor change as to press Ctrl + [ or ].
However, you have to make a change in Preferences, which will be described below.
Here is a 50 px brush at different hardness percentages.
Here are brush strokes of the 50 px brush at different hardness percentages.
When you press Shift + [ or ], you can't see the hardness change.
However, if you change a setting in Preferences, you can.
The circle of the brush cursor becomes more-and-more mottled as the hardness goes from 100%, none, to 0%, maximum feathering.
Below, the brush cursor shows the mottling due to the hardness of 0%, maximum feathering.
By default, the size of the brush cursor is 50% of the size of the brush.
Change the cursor size to 100%.
Then, you'll be able to see the mottled edge when the brush is feathered.
Do the following.
1) Go to Edit > Preferences (Windows) or Photoshop Elements > Preferences (Mac).
2) Click, on the left side, Display & Cursors.
3) In the Painting Cursors section, select Full Size Brush Tip.
As you press Shift + [ or ], to change the hardness, the brush cursor will be:
• Solid if the edge of the brush doesn't have any feathering.
• More mottled, as the feathering goes from 100%, none, to 0%, maximum feathering.