Adobe recently added two refinement sliders—Feather and Edge—into the Masking panel in both Lightroom Classic and the cloud-based Adobe Lightroom application. These additional controls let you fine-tune the boundaries of your selection after you create an AI mask using tools like Select Subject, Select Sky, or the People (Select Facial Features) masking options.
What Feather Does
Feather softens the boundary between the masked area and the unmasked background. Instead of an abrupt, hard transition, the edges of the mask fade gently into the rest of the frame.
A small amount of feathering cleans up the rough, pixelated fringes that automated AI selection algorithms occasionally generate. A little feathering is often a good addition but pushing this slider too far alters the mask dramatically. At higher values, Feather causes the mask to expand and diffuse, behaving much like the Gaussian Blur filter in Adobe Photoshop. At extreme values, an over-Feathered mask loses subject isolation entirely.
In practice, most images require only modest feathering—typically a few percentage points—rather than an aggressive slider push.
What Edge Does
Unlike Feather, the new Edge control shifts the mask’s boundary outward (expansion) or inward (contraction). Dragging Edge to a positive value expands the mask so that it covers additional pixels throughout the image. Dragging the Edge command to a negative value contracts the selection inward. This control is particularly helpful in two common scenarios:
- Overspill Cleanup: When an AI mask extends slightly beyond the area that you want to target, contracting the mask pulls the perimeter inward, protecting surrounding areas from unwanted adjustments.
- Eliminating Subtraction Halos: When using an AI tool in Subtract Mode to build a complex mask, Lightroom’s AI algorithms frequently leave behind a thin fringe or halo. Expanding the subtraction with a positive Edge value is an easy way to wipe out that residual halo.
Best Practice: How to Clearly See Edge Adjustments
Before touching either slider, make sure that you can actually see what is happening. Subtle shifts of just 1 to 3 pixels are often all that many masks require, yet these changes are very difficult to detect unless you zoom way in. In addition, using these features will help:
- Toggle Mask Overlay: Press “O” to turn the Mask Overlay on or off.
- Cycle Overlay Modes: Press “Shift + O” to cycle through the Overlay Display Modes. Switching to the Color Overlay on Black or the White on Black display often makes it easier to see the mask’s perimeter against a high-contrast background.
- The “Nudge” Method: Alternatively, dialing in an exaggerated Exposure or Tint shift while adjusting Edge or Feather makes boundary changes more obvious. Once the mask’s edges are perfect, reset these sliders and then make your desired changes.
Where Feather and Edge Help and Where They Fall Short
Crucially, Feather and Edge only modify existing boundaries; they cannot compensate for selections that are structurally incomplete. Both of these new sliders excel when an AI-powered mask has completely identified the intended subject and only the perimeter requires micro-adjustments.
If Lightroom’s Sky Masking tool, for example, fails to detect a pocket of sky between tree branches or within architectural openings, then adjusting Feather or Edge will not fill this void. Expanding the Edge in this case will simply cause the mask to cut into foreground elements, and overdoing it with the Feather command will introduce unnatural halos around the problem area.
When the underlying selection itself is flawed, Feather and Edge are the wrong tool for the job. In these situations, other features like the Add, Subtract, or Intersect mask commands are a better solution.
