Module 4 · Tone Curve, Masking & Dodge/Burn
Goal: use the tone curve for precise tonal control, apply AI and manual masks to restrict edits to subjects/skies/backgrounds, and use local dodge & burn to add depth and direct the viewer's eye.
📱 Use NotebookLM on your phone
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How to use NotebookLM here
Click "Copy YouTube links" and open NotebookLM. Add a photo description of a high-contrast scene (like Barcelona midday sun) as a text note — ask how you'd handle it with masking and curves.
Questions to ask NotebookLM:
- "How do I create a gentle S-curve without making midtones too dark?"
- "What's the difference between dodging and burning at the masking level vs the brush level?"
- "How do I use AI subject masking to expose the person correctly when the background is much brighter?"
- Scan QR code with your phone camera
- Click "Copy YouTube links"
- Open NotebookLM → create notebook → add sources
- Wait ~30 sec and start asking
Recommended videos
Key concepts
- Tone curve basics: x-axis = input brightness, y-axis = output brightness. A point on the diagonal = no change. Lift the shadow point up = raised black floor (cinematic fade). Pull highlights down = recovered bright areas. S-curve (lift midtones, lower shadows slightly) = the classic contrast boost.
- RGB curves: the master curve affects all channels. Individual R/G/B curves shift colour balance at specific tonal ranges — e.g. add red to shadows (Red curve: pull shadow point up) while cooling highlights (Blue curve: pull shadow point down). Foundation of colour grading (Module 6).
- Masking types in Photomator: Subject (AI person/object detection), Sky (AI background separation), Background (inverse of subject), Brush (manual paint), Gradient/Radial (feathered shapes), Colour Range (select by sampled colour), Luminance Range (select by brightness). Combine with Add/Subtract to build complex masks.
- When to use masking: any time the sky and foreground need different treatment; subject needs different exposure than background; you want to sharpen only the face; dodge/burn requires precision. Default: try global correction first — masking adds complexity.
- Dodge and burn: dodge = make lighter, burn = make darker. Used to guide the eye: darken corners/edges to vignette naturally; lighten the subject's face; add shadow to make a 3D shape feel. Use a very low flow brush (5–15%) and build up gradually. Aggressive D&B looks fake.
- Luminance masking: select only the bright or dark areas of the image. Useful for recovering skies (select highlights → pull down) without affecting dark foreground. More precise than a gradient mask when the horizon is uneven.
Self-check exercises
1. You have a Barcelona street photo where the subject is in shade but the bright sunlit background is correctly exposed. How do you fix the subject's exposure without blowing the background?
Approach with masking:
- Create a Subject mask (AI detection will select the person)
- Verify the mask — check edges, especially around hair and shoulders. Refine with a Subtract brush if needed
- With the subject mask active, raise Exposure +0.7 to +1.5 stops
- Add Shadows +20 to open the shadowed areas
- Check: the background should be unaffected. If the mask bleeds into the background, subtract the overflowing area with a brush
2. Draw (or describe) an S-curve that adds contrast without clipping highlights or crushing shadows. Where do you place the control points?
S-curve control points:
- Shadow anchor: at roughly 25% from the left (quarter-tone shadows) — pull down slightly (output ≈ 20%). This darkens the darker tones.
- Midpoint: leave the midpoint (50%,50%) approximately in place — you can nudge it up slightly to keep midtones bright
- Highlight anchor: at roughly 75% from the left — pull up slightly (output ≈ 80%). This brightens the brighter tones.
3. After dodging and burning a portrait, the edit looks unnatural — skin has obvious light and dark patches. What went wrong?
Most likely causes:
- Flow too high: each brush stroke is too strong. D&B should be built up in multiple passes at 5–10% flow. At 50%+ flow, each stroke is immediately visible.
- Hard brush: a hard-edged brush creates obvious transitions. Use a large, very soft brush (0% hardness) so the effect fades at the edges.
- Not following natural contours: D&B should reinforce existing light — darken where shadows naturally fall (under cheekbones, sides of nose, chin), lighten where light naturally hits (bridge of nose, forehead, cheekbones). Fighting the natural light looks fake.
- Too much coverage: D&B should be surgical — 10–20% of the image area at most. If you've painted most of the face, you've over-done it.