Photoshop’s Edit–>Fade Command
Immediately after applying just about any filter or adjustment command and after using many of Photoshop’s tools, you can adjust the effect with the Fade command, found under the Edit menu. (Keep in mind that Fade is available only immediately after using a filter, adjustment, or tool. You can’t even use the Save command in between.)
With Fade, you can reduce the opacity of the previous command or tool, thus reducing its impact on your image. You can also change the blending mode, which alters how the command or tool interacts with pixel colors prior to your change.
Say, for example, you paint a black stroke with the Brush tool set to Normal and 100% opacity. Immediately afterward, you choose Edit Fade Brush. You can then pick a new blending mode and/or reduce the opacity setting, which changes the painted stroke to appear as if you’d selected the new settings in the Options bar before painting.
You can also apply the Unsharp Mask (or Smart Sharpen) filter and then choose Edit→Fade Unsharp Mask, as shown in the figure here. (Yes, the Fade command changes names automatically!)
In the Fade dialog box, changing the blending mode from Normal to Luminosity ensures that your Unsharp Mask filter doesn’t alter the color of pixels along edges. Using the Fade command this way is the same as if you’d switched to Lab color mode and sharpened only the L channel — without having to switch color modes at all.
Note that the Edit→Fade command isn’t available when you’re working with Smart Filters. If you need to fade the filter, you can first choose Layer→Smart Objects→Rasterize and then apply the filter. You lose the advantages of working with Smart Objects and Smart Filters, but the Edit→Fade command will be available.