While clipping paths are well-known in Adobe Illustrator, opacity masks allow more complex clipping patterns.
Illustrator Clipping Paths
Clipping paths rely on simple, solid shapes. A group of shapes creates odd intersections of the clipped content, so designers must combined them. Additionally, the clipping mask applies evenly across the clipping path, because they ultimately ignore colors and gradients. Blending modes like Screen can mimic a gradient clipping mask, and blending mode settings like Knockout can prevent the blend mode from interfering with other styles. However, the layers and blend modes involved might complicate making clipping paths.
Illustrator Opacity Masks
Opacity masks permit more complex clipping paths because they don’t gradients. Instead, black hides content while white reveals it. This works the same way Layer Masks do in Photoshop, just with vector shapes. One use of opacity masks is fading a photo over a complex background, when a gradient from opaque to transparent covers too many details. Use a similar effect to create the sense of a reflective surface as well by repeating the content as a fading “shadow.” Also consider opacity masks to create a vignette effect in Illustrator without the use of Photoshop.
Making an Illustrator Opacity Mask Step-by-Step
Making an opacity mask in Illustrator is easy. First, select the object you wish to clip.
Then, in the Menu bar, click the text for Opacity to reveal a small panel. The panel displays two thumbnails: the active object on the left and on the right an empty gray thumbnail. Hovering over the empty thumbnail reveals the instructions, “Click to create and edit an opacity mask.” Double-click the thumbnail or hit the button that says “Make Mask” to create an opacity mask on top of the active object.
The active object now appears hidden from view.
Next, draw a shape in white to reveal the content so edits are more visible. Apply Illustrator’s preset White, Black gradient to apply a fading clipping mask to the active object. You can edit the gradient stops like normal, or move anchors to redraw the shape as needed.
Once satisfied with the way it looks, you’ll need to exit the opacity mask editing mode.
Leave the opacity mask editing mode by first returning to the Menu bar > Opacity. Then double-click the left thumbnail of the active content. Now the rest of the art board and pasteboard is visible and editable again.
The strategic combination of clipping paths and opacity masks allows for more complex layering in your Illustrator documents. If the document requires a lot of raster graphics and even more complex masks, then try importing the vector objects from Illustrator into Photoshop as Smart Objects and work with Layer Masks in Photoshop.