Adjusting Layer Opacity

Every layer that you add to a composition shares a specific relationship with the other layers surrounding it in the Layers palette. One very straightforward way that you can blend layers together and control the way they interact is by adjusting each layer’s opacity level. To understand layer opacity, it helps to think of layers as the building blocks of your Photoshop composition. Painting with oil paint on a canvas is a good analogy. To paint your masterpiece, you must add paint to the canvas and blend colors together along the way. Doing so helps to unify the overall image. The same principles apply when you’re creating a layered composition in Photoshop. Consider the layers that you’re adding as your oil paint and the document window as your canvas. You can use the Opacity control in the Layers palette to blend layers together and unify your image.

Located at the top of the Layers palette, the Opacity control allows you to make a selected layer completely or partly transparent. By default, all new layers added to a composition are set to 100% Opacity. Lowering the opacity value allows you to see through to the layers underneath in the stack. You can lower the opacity value of a selected layer in the palette either by entering a number in the Opacity field or by clicking the arrow to the right of the field and dragging the pop-up slider control to the left.

Scrubbing
You can also raise or lower dynamic field values in the Photoshop interface by using a technique called scrubbing. Start by hovering the cursor over the field label, such as Opacity in the Layers palette. When the cursor changes to  display a hand with left/right arrows on either side of it, click and drag to the left (to decrease) or right (to increase). To adjust values in 10% increments, hold down the Shift key as you click and drag.

You can adjust the opacity value of a selected layer in 10% increments by using the number keys or the numeric keypad. To change the value by using this method, access any tool that does not have its own opacity settings in the Options palette, such as the Move tool, and then press 1 to apply a value of 10%, 2 for 20%, 3 for 30%, and so forth. Press 0 to apply a value of 100%. You can also type two numbers quickly in succession to apply a specific value (for example, typing 85 applies a value of 85%). You can adjust the opacity value of only a single selected layer at a time. You cannot adjust the opacity value for multiple selected layers. You can adjust opacity values for multiple layers in a group by selecting the group layer (the folder in the Layers palette) and  lowering its opacity value.