Photography 04: Gentle S-Curves in DxO PhotoLab
Lesson 4 of 12
By Sourov Deb. I am a DxO ambassador. DxO did not author this. No DxO approval is implied.
Tap the paper scene
Goal
Increase tonal separation. Keep useful edge detail.
Concept first
A diagonal curve stays neutral. An S-curve increases contrast.
Lower shadows slightly. Lift highlights slightly. Midtones spread farther apart.
Large moves compress edges. Texture can disappear. Small moves protect detail.
Before and after
Flat: 64 maps to 64. 191 maps to 191.
Gentle S: 64 maps near 51. 191 maps near 204.
Black stays at zero. White stays at 255. Mid-gray stays near 128.
This example is simulated. It is not PhotoLab output. Values teach direction only.
What changed?
Dark tones became darker. Bright tones became brighter. Midtone separation increased.
Why? The curve became steeper. Steeper sections separate neighboring tones.
Try it in PhotoLab
- Open Customize, then Light.
- Open Tone Curve. Choose L.
- Add shadow and highlight points.
- Move them gently down-up.
- Check Histogram and clipping.
Use the Histogram palette. Its result includes corrections. Enable clipping indicators.
Choose strength by image. No number works universally.
Common mistake
Making a dramatic S. Shadow texture becomes cramped. Highlight texture also compresses.
Short exercise
Choose textured shadows. Find textured highlights. Build a gentle S. Then compare flat.
Answer and self-check
- Midtones should separate.
- Shadows retain texture.
- Highlights retain texture.
- Clipping indicators stay quiet.
- The curve stays gentle.
Lost texture means excess. Reduce both point moves.
Captioned demonstration
Transcript
00:00–00:07 — Flat tones can merge. Watch darks and lights.
00:07–00:15 — More contrast can erase detail. Protect useful textures.
00:15–00:23 — Lower one shadow point. Lift one highlight point.
00:23–00:31 — Shadows move downward. Highlights move upward.
00:31–00:40 — Midtones spread apart. Contrast increases.
00:40–00:48 — Open Customize, then Light. Open Tone Curve. Choose L.
00:48–01:00 — The diagonal changes nothing. Add two gentle points.
01:00–01:13 — Lower shadows slightly. Lift highlights slightly.
01:13–01:25 — Gentle S separates tones. Texture remains visible.
01:25–01:34 — Find shadow texture. Find highlight texture.
01:34–01:42 — Watch Histogram palette. Enable clipping indicators.
01:42–01:50 — A strong S compresses detail. Reduce both moves.
01:50–01:56 — Compare flat and gentle. Keep useful textures.
01:56–02:00 — Down shadows. Up highlights. Small moves preserve detail.
Visual: Gentle S-Curve
Tone Curve (Luminance)
Highlights ↑
╱
╱ ← gentle lift
╱
╱──────── Midtones (spread)
╲
╲ ← gentle lower
╲
Shadows ↓
Diagonal = neutral. S-shape = more separation, texture kept if gentle.
TED-style takeaway: A gentle S-curve is like speaking with more contrast in your voice — the important tones stand out, but you don’t shout and lose the quiet details.
Related tutorials: Photography 03: Tone Curve Foundations · Photography 02: Contrast
Version notes
Checked 7 October 2026. The guide describes PhotoLab 10. Tone Curve sits under Light. L changes luminance. Color stays preserved.
The curve background stays referential. The Histogram palette updates fully.
The tutorial shows PhotoLab 9. At 04:32–04:44, it opens curves. It selects luminance. Highlights move upward. Shadows move downward.