How Do I Do That in Photoshop?

Fix Washed-Out Skies?

Get the Graduated Filter tool (G; it has the same basic settings as the Adjustment Brush, but it’s not actually a brush—you click-and-drag it in a direction) from the toolbar, and start by resetting all the sliders to zero (double-click on the – [minus sign] button to the left of Exposure to set it to –1.00 and reset all the other sliders to zero). Now, take the tool and click-and-drag from the top of the image down to the horizon line, and it darkens the top, then gradually fades down to transparent, like a real neutral density ...