Abstract (30 sec). Great charts aren’t pretty; they’re perceptually efficient. Use preattentive cues, luminance over hue, and small multiples to answer one question per view—with uncertainty visible. Design for decisions, not decoration.

Overview (2 min) - **Premise.** The visual system is fast but picky: some encodings “pop,” others require reading. - **Implication.** Encode what matters with **position, length, and luminance**; reserve color for grouping. - **Practice.** Ask a question; choose one visual grammar that answers it; show uncertainty; annotate the takeaway.

1) Preattentive features: what pops in ~200 ms

  • Fast channels: position on a common scale, length, orientation, luminance contrast.
  • Slower or risky: area, angle, rainbow palettes.
  • Rule of thumb: make the answer live on a fast channel (e.g., position or length).

Debug test: Blur the chart to 10–20 px. Does the pattern still read? If not, you’re over‑encoding.

2) Gestalt & grouping: help the eye chunk

  • Use proximity and similarity (consistent hues/weights) to bundle related traces.
  • Leverage enclosure (light boxes) for subpanels instead of heavy gridlines.
  • Remove chart junk; emphasize data ink.

3) Color & luminance: show structure, not noise

  • Prefer luminance steps for magnitude; use hue to label categories.
  • Avoid more than ~6 categorical hues; add direct labels to cut legend scanning.
  • Ensure dark‑mode and color‑blind safe contrasts.

4) Small multiples > everything in one plot

  • If you’re answering “how did X change across A, B, C?”, show aligned small multiples.
  • Keep axes consistent; share zero baselines where meaningful; annotate the local story.

5) Uncertainty belongs on the page

  • Use bands, intervals, and counts; avoid false certainty.
  • Summaries should say “estimate ± interval” rather than a single number.
  • Consider scented interactions (hover reveals data density or intervals).

6) Question‑first layout

Write the question first, then pick an encoding:

  • “Are we improving week‑over‑week?” → aligned line charts with weekly deltas and a reference band.
  • “Which cohort underperforms?” → sorted bars with direct labels; highlight the cohort of interest.
  • “What changed after the intervention?” → pre/post small multiples with annotations.

7) A minimal style guide (copy/paste)

  • Title answers the question; subtitle names scope and date window.
  • One highlight color; everything else gray.
  • Direct labels on endpoints; legends only when necessary.
  • Tight y‑axis bounds with clear zero handling; gridlines faint.
  • One callout box per chart: “So what?” in a sentence.

8) From notebook to product without tears

  • Spec the view as question → encoding → interaction → annotation.
  • Add unit tests for transforms that feed charts (no silent data shifts).
  • Ship a print‑safe version (leaders still circulate PDFs).

Downloadables (optional)

  • “Question → Encoding” crib sheet (PDF)
  • Color & contrast checklist (PDF)
  • Small‑multiples starter (PNG templates)

CTA. Want the crib sheet? Email me and I’ll share the kit I use when building decision dashboards.