Localized Adjustments & Masking: Brush, Linear, Radial & Range Masks

Visual saliency — the eye's routing algorithm. Human gaze is not democratic. Eye-tracking research shows attention is captured, in roughly descending order of force, by: faces and eyes (dedicated neural hardware — the fusiform face area — fires for them involuntarily), regions of highest local contrast, the brightest areas (in a generally dark field), the sharpest detail, the warmest and most saturated color against cooler surroundings, and leading lines that promise direction. Every one of those levers is a Lightroom slider — which means masking is literally the engineering of eye movement: raise contrast, brightness, warmth, and sharpness where you want the entry point; suppress them along the exits. A vignette works not because darkness is pretty but because it lowers the salience of the frame edges, collapsing the probability that the eye wanders off-canvas.

Local dynamic range — the mask as a private exposure. Chapter 2 established that scenes out-range displays. Global compression (Highlights/Shadows) squeezes everything by one rule; masking instead grants each region its own tonal allocation — a −1 EV sky and a +0.7 EV foreground coexisting in one frame, exactly as the eye's own local adaptation would have perceived the scene on location. This is the honest defense of heavy local editing: the unedited file is often less faithful to perception than the masked one, because the sensor lacks the retina's regional gain control.

Feathering — the mathematics of invisibility. A mask is a grayscale map: white = full effect, black = none, grays = partial. The eye is ruthlessly good at detecting edges in adjustment strength, and nearly blind to gradients of it. Feathering interposes a smooth opacity ramp across the mask boundary so the adjustment fades below the retina's edge-detection threshold. The universal law of local editing follows: the stronger the adjustment, the wider its feather must be — a +1 EV dodge with a hard edge is a glowing stain; the same dodge feathered across a broad falloff is simply "better light."

The Masking panel (rebuilt in 2021 and expanded since) offers three families of selection, all combinable:

AI segmentation masks. Select Subject, Select Sky, Select Background, Select Objects (paint or box a region and the model snaps to the object), and Select People — which further decomposes each detected person into Face Skin, Body Skin, Eyebrows, Eye Sclera, Iris & Pupil, Lips, Teeth, Hair, and Clothing. These models return in seconds selections that took Photoshop masters hours, and they are re-computable: the mask updates its develop settings live like any other.

Geometric masks. The Linear Gradient applies a smooth ramp between two parallel lines — the classic graduated sky filter, now aimable in any direction. The Radial Gradient applies an ellipse with adjustable feather, invertible to affect inside or outside — the modern vignette, spotlight, and subject-glow tool. The Brush paints selection by hand with four parameters that beginners perpetually confuse: Size (diameter), Feather (soft border as a fraction of the diameter), Flow (the rate at which each stroke deposits effect — at Flow 20, repeated passes build density gradually like airbrushing), and Density (the ceiling of opacity a stroke may ever reach). Auto Mask confines strokes to areas matching the color/edge under the crosshair — miraculous along foliage against sky, jittery on noisy textures. Every mask accepts an Erase brush for corrections.

Range masks — selection by physics. Luminance Range selects pixels by brightness: a two-handled range with falloff ramps on each side, plus a Show Luminance Map overlay for aiming. Color Range selects by hue via eyedropper (Shift-click to gather up to five samples) with a Refine slider widening or tightening the chromatic net. Depth Range selects by distance where a depth map exists (computational smartphone captures). Range masks shine brightest in combination: every mask can have components Added, Subtracted, or Intersected (via the mask's context/… menu, "Intersect Mask with…"). Intersection is the professional's move — Select Sky ∩ Luminance(top 25%) touches only the bright clouds and never the blue; Select Subject ∩ Color Range(skin sample) isolates skin without one brushstroke.

Seeing the mask. Press O to toggle the overlay (default translucent red — Lightroom's traditional rubylith, echoing darkroom masking film) and Shift+O to cycle overlay styles (color overlay, image on black, image on white, white on black), because a red overlay is useless on a red dress. Each mask carries nearly the entire develop vocabulary privately: Exposure through Blacks, Temp and Tint (local white balance — Chapter 3, Recipe 4), Texture/Clarity/Dehaze, Saturation, Sharpness, Noise, and a local point Curve and Hue shift. A mask is, in effect, a second Lightroom aimed at a region.

Recipe 1 — The portrait dodge & burn (fifteen minutes to mastery):

1. 01Create Mask → Brush. Settings: Feather 75–90, Flow 15–25, Density 100, Auto Mask off. Set Exposure +0.3 before painting so strokes preview live.
2. 02Dodge mask: build luminance gradually (multiple low-flow passes) on the forehead center, cheekbone tops, bridge of nose, chin, and the iris of each eye. Final strength typically lands at Exposure +0.2 to +0.5.
3. 03Burn mask (new Brush, Exposure −0.2 to −0.5): temple sides, under cheekbones, jaw edges, sides of the nose — the sculptor's shadow map.
4. 04Eyes: two small Radial masks over the irises — Exposure +0.2, Saturation +5 to +10, Sharpness +15; more than this manufactures the dreaded husky-eye.
5. 05Environment: Radial mask around the subject, inverted, with Exposure −0.3 to −0.6, Clarity −5 to −10, Saturation −5 — the room recedes, the face advances. Press O frequently; if any mask edge is visible as an edge, widen the feather.

Recipe 2 — Sky drama without sky replacement:

1. 01Select Sky. Baseline: Highlights −30 to −60, Dehaze +10 to +25, Temp −200 to −400 K, Saturation +5 to +10.
2. 02Inspect the horizon and any trees/hair crossing the boundary at 100%; the model is excellent but not divine. Subtract with a small brush where halos threaten.
3. 03For clouds only: duplicate the sky mask and Intersect with Luminance Range set to the upper quarter — now burn the cloud bellies (Highlights −40) or ignite their tops (Whites +20) independently of the blue.
4. 04Ground handshake: a Linear Gradient rising from the bottom with Shadows +20, Exposure +0.2 so the newly dramatic sky doesn't orphan a murky foreground.

Recipe 3 — Subject pop (the two-mask separation):

1. 01Select Subject: Exposure +0.15 to +0.3, Texture +5 to +15, Clarity +5.
2. 02Select Background (or duplicate-and-invert the first): Exposure −0.2 to −0.5, Clarity −10 to −20, Saturation −5 to −15, Sharpness −20.
3. 03The frame now contains a sharp, bright, crisp, warm zone and a soft, dark, muted one — all four saliency levers of §6.1 pulling in the same direction. Restraint check: view at fit-to-screen; if you can see the technique, halve everything.

Recipe 4 — Zone-targeted color grading (the range-mask grade): create a Luminance Range mask holding only the shadows (lower third, generous falloff) and give it Temp −300 K plus a local curve blue-channel lift; a second Luminance mask on the top quarter receives Temp +200 K. This is Chapter 5's teal-and-orange executed with surgical zone control — many colorists prefer it to the grading wheels precisely because the luminance boundaries are theirs to draw.