Sharpen Effect

A professional sharpen tool (that won’t destroy your image)

Most “sharpen” filters are a single slider that easily creates:

• white halos around edges
• crunchy noise in shadows
• color fringing (red/green/blue outlines)

This Sharpen tool is built like a real editing control panel. You get the classic pro parameters—Amount, Radius, Threshold—plus two extra safety features that make the results cleaner:

• Halo Limit — clamps edge boosts so you don’t get that over-sharpened rim
• Luminance Mode — sharpens brightness detail only to avoid color halos

Everything runs locally in your browser for privacy.

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Workflow & usage

1. Add an image Drag & drop, click to select, or paste (Ctrl/⌘ + V). EXIF orientation is respected.

2. Pick your goal

   • Crisp detail (hair, textures, architecture) → small Radius
   • Clarity / punch (mid-size contrast) → large Radius, lower Amount

3. Adjust Amount + Radius These two define the “strength” and the “size of detail” being enhanced.

4. Use Threshold if noise appears Increase it until grain/noise stops getting sharpened.

5. Use Halo Limit if edges get outlined Lower limit to clamp the halos.

6. Keep Luminance Mode on (recommended) It’s the easiest way to keep sharpening clean.

7. Download Export full resolution in the original file format.

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What sharpening really is (Unsharp Mask explained)

Despite the name, most sharpening is based on Unsharp Mask (USM):

1. Make a blurred copy of the image
2. Subtract the blur from the original → this isolates edge detail
3. Add that detail back (scaled by Amount)

That’s why sharpening increases contrast at edges: it literally boosts the difference between pixels.

The three classic controls

• Amount: how much edge contrast you add
• Radius: how wide the edge boost is (detail size)
• Threshold: how big a difference must be before sharpening applies (noise masking)

This tool adds:

• Halo Limit: a safety clamp on the edge boost
• Luminance Mode: do the boost on brightness only

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Sharpen vs Clarity (same engine, different settings)

Sharpen (fine detail)

Targets small edges.

• Radius: ~0.5–2px
• Amount: ~80–250%
• Threshold: 5–15 (often)
• Halo Limit: lower (stricter) to avoid crunchy rims

Clarity (large-radius punch)

Targets broader transitions and gives a “presence” boost.

• Radius: ~10–40px
• Amount: ~30–80%
• Threshold: 0–5
• Halo Limit: can stay higher

If your image looks “crispy” and noisy, you’re in sharpen territory. If it looks “punchier” and more dimensional, you’re in clarity territory.

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Controls explained

Amount (0–300%)

How strongly edges are boosted.

• 0–60%: subtle polish
• 60–150%: typical sharpening
• 150–300%: strong / corrective (watch halos)

Rule of thumb: if you increase Radius, decrease Amount.

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Radius (0.5–50px)

The size of the detail being emphasized.

• 0.5–1.0px: tiny detail (fine hair, micro texture)
• 1–2px: general photo sharpening
• 2–6px: “crunchy” if Amount is high (use threshold/limit)
• 10–50px: clarity/presence look (use lower Amount)

Tip: Radius is the most important knob for how sharpening feels.

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Threshold (0–50)

Noise masking: ignores small differences.

• 0: sharpen everything (including noise)
• 5–12: good general noise protection
• 12–25: portraits / skin-friendly sharpening
• 25+: very selective sharpening

If shadows get grainy or skin looks gritty, raise Threshold.

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Halo Limit (0–100)

Prevents harsh white/black outlines by clamping the maximum per-pixel change.

• 100: no limit (classic unsharp mask behavior)
• 40–80: safer, cleaner edges
• 10–40: strong halo protection (great for high Amount)
• 0: effectively disables changes

When to reduce it: if you see bright rims on edges, especially around high-contrast lines (buildings, text, branches).

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Luminance Mode (recommended)

When enabled, sharpening is applied to brightness (perceived luminance) instead of sharpening R/G/B separately.

Why it matters:

• RGB sharpening can create color halos (chromatic fringing)
• Luminance-only sharpening tends to look cleaner and more “photographic”

Keep this ON unless you have a specific reason to sharpen color edges.

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Quick presets (copy these settings)

Everyday photo sharpen (clean)

• Amount: 80–140%
• Radius: 1.0–1.8px
• Threshold: 5–12
• Halo Limit: 35–70
• Luminance: ON

Strong detail (architecture / product)

• Amount: 160–260%
• Radius: 0.7–1.5px
• Threshold: 0–8
• Halo Limit: 20–50
• Luminance: ON

Portrait-safe sharpen (avoid skin grit)

• Amount: 60–120%
• Radius: 1.2–2.5px
• Threshold: 12–25
• Halo Limit: 30–70
• Luminance: ON

Clarity / presence boost (large-radius)

• Amount: 35–75%
• Radius: 15–35px
• Threshold: 0–5
• Halo Limit: 70–100
• Luminance: ON

“Fix soft focus” (careful)

• Amount: 200–300%
• Radius: 1.0–2.5px
• Threshold: 8–18
• Halo Limit: 15–40
• Luminance: ON

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Best-result tips

• Zoom mentally, not literally. Sharpening should look good at normal viewing size. If you optimize for extreme zoom, it can look harsh.

• Radius first, Amount second. Pick the detail size with Radius, then dial Amount to taste.

• Use Threshold to keep noise under control. Grain and sensor noise are basically “tiny edges.” Threshold stops you sharpening them.

• Halo Limit is your safety net. If your result looks digital or outlined, lower Limit.

• Don’t sharpen already-compressed images too hard. JPEG artifacts can become more visible with extreme settings.

• Optimize after export Run results through Image Compressor or Progressive JPEG Converter for production-ready sizes.

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When sharpening is the wrong tool

Sharpening boosts edges; it doesn’t truly add missing information.

• Motion blur / camera shake: needs deblur techniques (not included here)
• Heavy noise: consider denoise first, then sharpen lightly
• Very low-res images: sharpening can reveal block artifacts; try subtle settings

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How it works (matches the engine)

This tool implements a fast, pro-style Unsharp Mask pipeline:

1. Decode the image locally (Canvas)
2. Create a blurred version using a 3-pass box blur (fast Gaussian approximation)
3. Compute the difference (original − blur) to isolate edges
4. Apply Amount to scale that difference
5. Apply Threshold so small differences (noise) are skipped
6. Apply Halo Limit to clamp the maximum change per pixel
7. Optionally apply in Luminance Mode (brightness-only sharpening)

Preview vs export: preview is rendered at capped resolution for speed; export runs at full original resolution.

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Troubleshooting

• I see white outlines around edges Reduce Amount, reduce Radius, or lower Halo Limit (stricter clamp).

• Shadows look grainy / noisy Increase Threshold, and consider lowering Amount.

• It looks crunchy or “HDR-ish” You likely have too much Amount for the chosen Radius. Reduce Amount or lower Radius.

• Colors look fringed (rainbow edges) Turn Luminance Mode ON.

• Small text/details look worse Use smaller Radius (0.5–1.2px) and stricter Halo Limit.

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Glossary

• Unsharp Mask (USM): classic sharpening by subtracting a blur and adding edges back.
• Halo: bright/dark outline created by too-strong edge contrast.
• Threshold: minimum difference required before sharpening applies.
• Luminance: perceived brightness (how light/dark a pixel looks).
• Clarity: large-radius local contrast boost (a “presence” look).