In addition to setting opacity, which affects any layer styles and blending modes applied to the layer, you can specify a fill opacity for layers. Fill opacity affects pixels painted in a layer or shapes drawn on a layer without affecting the opacity of any layer effects that have been applied to the layer.
For example, if your layer contains a drawn shape or text that uses a drop shadow layer effect, adjust the fill opacity to change the opacity of the shape or text itself without changing the opacity of the shadow.
In the Layers palette, enter a value in the Fill Opacity text box or drag the Fill Opacity pop‑up slider.
Double-click a layer thumbnail, choose Layer > Layer Style > Blending Options, and enter a value in the Fill Opacity text box or drag the Fill Opacity pop-up slider.