EdgeDetect

Read EdgeDetect as a four-stage pipeline. Mode decides which differences participate in detection: RGB Edges responds to color and brightness changes, while Grayscale Edges responds only to brightness changes. Detection shapes the contour, Filters prepares the source and selects edge polarity, and Advanced Options stabilizes or limits output values.

The result is a new image pass, not the untouched source with an automatic semantic outline. With Edge Mask Overlay disabled, the Viewer shows only the detected edges. If you want those edges back over the source, keep a separate source branch and composite the processed edge pass through Glow/ColorCorrector and Merge.

RGB Edges is the default mode and derives boundaries from both color and luminance differences, so saturated graphics can create chromatic contour responses. Grayscale Edges derives boundaries from brightness changes only; in this mode the conditional Edge Color control becomes available to colorize the generated outlines.

Edge Width controls contour thickness, Brightness controls the brightness of the resulting edges, and Gamma reshapes mid-strength response. Brightness is not a detection threshold. Blackmagic documents gamma below 1 as brightening mid-strength edges so more become visible, while gamma above 1 darkens mid-strength response and reduces the pass toward only the strongest detected boundaries. Blur then softens the final result.

Edge Mask Overlay is a diagnostic view that overlays detected contours on the current frame. It is particularly useful before Glow because a dirty edge pass becomes even more obvious after bloom. Overlay is a setup aid, not a separate matte input or a substitute for the final composite.

Preprocess has three states. None performs no extra preparation. Filter reduces texture and detail and reveals the conditional Scale control. Flatten smooths relatively uniform image regions while preserving boundaries between flatter regions and reveals the conditional Strength control. Scale and Strength therefore belong to different conditional branches and should not be documented as permanently visible together.

Half-Edges Only selects edge polarity rather than line thickness. None keeps both sides. Keep Light Side retains the brighter half of a brightness transition and can be useful for light-wrap-style work. Keep Dark Side retains the darker half and can create a halo outside a bright subject. Either one-sided mode reveals the conditional Half-Edge Gain control for boosting the retained half independently of the main Brightness control.

Normalize Per Frame adjusts each incoming frame toward a consistent edge brightness so contours stay visible while the scene changes brightness or flickers. That can be useful on unstable material, but it changes gain from frame to frame, so it must be judged in playback rather than on a single still. If the shot is already stable, automatic normalization may be unnecessary.

Clamp Brightness prevents output edges from becoming excessively bright on high-contrast material. It is especially useful before Glow or additive compositing, but it does not clean a noisy detector or choose better boundaries. Solve source/preprocess/gamma/polarity problems first, then clamp extreme output values when required.

Effect Mask is a separate standard Fusion mask input. It limits where the calculated effect contributes spatially; it does not decide what qualifies as an edge. If the background creates unwanted lines, a mask can hide them outside the subject, but noise and texture inside the selected area still participate in EdgeDetect unless the image itself is prepared appropriately.

EdgeDetect is particularly useful as an intermediate technical pass. Grayscale edges can be converted through Bitmap into a true mask stream, used as a local correction driver, fed into Glow, Erode/Dilate or Displace, or processed as a visible design layer. An image edge pass and a mask stream are different data types, so convert explicitly when a downstream port expects a mask.

All four archived Inspector captures genuinely show EdgeDetect. Controls shows RGB Edges selected, Edge Width 0.200000, Brightness 2.5, Gamma 1.0, Blur 0.0, Edge Mask Overlay off, Preprocess None, Half-Edges Only None, Normalize Per Frame off, and Clamp Brightness on. These are observed values in one capture, not a universal preset.

In the archived dropdown captures, Grayscale Edges, Filter, Flatten, Keep Light Side and Keep Dark Side appear grey. The Resolve 21 manual documents these algorithms and their conditional controls, but the images alone do not prove that these choices are selectable in the installed build. If unavailable, retain RGB / None and mark the experiment as awaiting live validation.

The Settings tab exists in the archived Controls capture but is not open. The fields and active switches in this build are not verified. Do not copy a generic Fusion Settings list from a different tool and present it as a captured EdgeDetect Inspector.

Inspect RGB and alpha separately. EdgeDetect produces an image edge pass; its dark background is not necessarily transparent when sent to Merge.Foreground. Before layering over footage, inspect output alpha and, if needed, use Bitmap to create an explicit matte for the chosen image branch. An image output must not be treated as an implicit mask-only stream.

Normalize Per Frame and Clamp Brightness serve different roles: one changes gain across frames, the other limits excessive edge brightness. For a controlled temporal test, run two matched EdgeDetect branches into a Dissolve and compare at exactly 0/1 on matching frames; judge stabilization in playback, not from a still.