AutomaticDirtRemoval

Automatic Dirt Removal is a Studio-only Resolve FX Revival tool. It is not a general denoiser and not a cosmetic blur: it targets temporally unstable local defects such as dust, dirt, hairs, tape hits and similar damage that exists briefly and then disappears.

Blackmagic describes the core process as optical-flow temporal analysis. The effect compares the current frame with neighboring frames, estimates real scene motion, and tries to distinguish short-lived contamination from legitimate image detail that simply moved between frames.

A useful mental split is detection first, repair second. Motion Est. Type, Neighbor Frames, Dirt Size Threshold, Motion Threshold and Edge Ignore primarily change what the detector considers dirt; Repair Strength determines how strongly the already-detected candidates are reconstructed.

Motion Est. Type has four documented modes: None, Faster, Normal and Better. These are not creative presets. They trade processing cost against motion-analysis quality: None avoids motion compensation, Faster prioritizes speed, Normal is the main balance, and Better spends more computation on a more reliable match.

Neighbor Frames sets the temporal depth used during detection. More neighboring frames provide more evidence for transient dirt but take longer to process. The captured Resolve 21 Inspector on this page shows 2; treat that as UI evidence, not as a universal preset.

Repair Strength does not by itself decide whether a pixel is dirt. It controls how aggressively detected candidates are repaired. If the repair mask is wrong, raising Repair Strength generally makes the wrong repair stronger rather than fixing detection.

Dirt Size Threshold is critical for preserving film grain. Blackmagic explicitly notes that raising the threshold can omit fine texture such as film grain from the operation, but may also let smaller pieces of dirt pass through. If grain is being attacked, adjust size detection before simply reducing Strength.

Show Repair Mask is the primary diagnostic mode. It reveals which regions the effect currently believes are defects, making false positives on grain, highlights, edges or moving texture much easier to see than they are in the final image.

Motion Threshold controls the point at which unstable/moving pixels can be classified as dirt or artifacts. The documented tradeoff is deliberate: lower values can leave more dirt but produce fewer motion artifacts; higher values remove more dirt but increase the risk of damaging real motion.

Edge Ignore protects strong real image boundaries. Higher values exclude more hard edges from repair. It is particularly useful around text, architecture, hair, lashes, wires and other high-contrast features that a temporal detector can mistake for damage.

Automatic Dirt Removal is strongest on short-lived contamination. Blackmagic specifically warns that it is less successful on vertical scratches that remain in the same position for multiple frames and ineffective on persistent dirt on the lens. Those defects do not provide the transient behavior this tool expects.

That limitation defines the boundary with Dust Buster, Paint/Clone and Patch Replacer. Automatic Dirt Removal is excellent as an automatic first pass over many transient spots; difficult persistent or isolated defects are often more predictable with targeted manual repair.

Fast motion must be judged over time, not on a hero still. Optical-flow mismatch can create swimming texture, soft patches, repeated fragments or loss of genuine detail. Final QC should include playback and frame stepping through the hardest movement.

On film material, grain is image texture rather than a detector error. If Show Repair Mask lights up across the whole frame with tiny candidates, detection is too permissive: Dirt Size Threshold may be too low, Motion Threshold may be too high, or Repair Strength may be exaggerating an already-bad selection.

In Fusion, use the blue Effect Mask as spatial coverage for the final effect. It can confine restoration to the damaged region and protect clean areas. Do not describe it as a guaranteed selector for the effect's internal temporal statistics without live verification on the target Resolve build.

The captured Inspector on this page shows Normal, Neighbor Frames 2, Repair Strength around 0.9, Dirt Size Thr. 0.1, Motion Thr. 100 and Edge Ignore 0. Those numbers prove the current labels and grouping, not a ready-made recipe for every scan, resolution or motion pattern.

A reliable production order is: choose motion estimation and temporal radius, inspect Show Repair Mask, tune size/motion/edge protection, then dose Repair Strength, disable the diagnostic view and review the complete shot in motion.

The final criterion is stable restoration without structural damage, not the maximum number of removed spots on a single frame. If cleanup starts erasing texture, edges or motion, leave some dirt for manual repair rather than turning the automatic pass into a new artifact generator.