HQDN3D

The fast all-rounder. A spatial filter with light temporal averaging — the algorithm you should start with almost every time.

What it does

Cleans luma and color with two mechanisms at once: it blurs fine noise inside the frame and slightly averages with neighboring frames. It works fast, predictably, and equally well across the whole timeline.

When to pick it

• You need a result in a minute, not in an evening.
• There is a lot of footage and speed matters (drafts, large projects, concerts).
• The noise is weak or medium.
• The frame has motion and you don't want to spend time setting up block-based algorithms.

When not to pick it: very heavy noise (it can't cope), or footage where textures and detail matter above all (it will smooth them more than NLMeans/BM3D).

Parameters in plain words

In Simple mode, HQDN3D leaves you the Denoise (Luma), Chroma and Balance sliders — see the basic guide. In Advanced you see four sliders:

• Luma Spatial — how hard to clean luma inside the frame. The main luma slider. Higher — cleaner, but softer.
• Chroma Spatial — the same for color (color speckles, rainbow smears in the shadows). Color noise is usually more noticeable than luma noise, and it is often removed more aggressively.
• Luma Temporal — how strongly to average luma with neighboring frames. Higher — cleaner static shots, but stronger ghosting on motion.
• Chroma Temporal — the same for color.

A rule that settles most questions: Spatial is responsible for softness, Temporal for ghosting. Soft → Spatial to the left. Ghosting → Temporal to the left or Balance to the left (and turn on Motion Compensation).

All four share the same range — from 0 to 15. But the strength per unit differs: Spatial is 2.5 times "hotter" than Temporal (its value is multiplied by 2.5 inside the filter), so the same number gives stronger smoothing inside the frame than between frames. Hence the rule: comparing Spatial and Temporal by the number is pointless — look at the picture.

How it works inside

The filter estimates the "noisiness" of each pixel from its neighborhood: where the neighborhood is uniform, the pixel looks like noise and is blurred more strongly; where there is an edge (an object boundary, a texture), it is blurred less. The spatial part does this inside the frame, the temporal part does it between neighboring frames with motion compensation. Luma and Chroma are handled by independent parameters, because color noise lives "its own" life and often needs a different strength.

If it didn't help

• Soft, plastic skin → Luma Spatial to the left; consider NLMeans or BM3D.
• Ghosting on motion → Luma Temporal to the left, Balance to the left, Motion Compensation → Enable.
• Noise remains → the noise is stronger than HQDN3D can handle: add a second slot (BM3D or FFTdnoiz) or switch to BM3D/BM4D.
• Detail got eaten → NLMeans / BM3D.

Next — FAQ or the next algorithm: ATAdenoise.