Editing Techniques with Filters
You can apply a filter to only a portion of an image by first selecting the portion of the image to apply it to before launching the Filter Gallery. Apply a feather to the selection by choosing Select > Feather if a more seamless transition between the area with the filter and that without it is required.
Like other Photoshop tools, when you apply a filter, the Fade option appears on the Edit menu. Use this option to vary the opacity of the filter and to change its blend mode so it affects the image differently. These Opacity and Blend Mode options are not available on the Filter Gallery menu.