ARBE λ* (Absorption–Reflection Balance Edge) is the wavelength where a color absorbs and reflects light equally—a physical fingerprint of color, more reliable than visual appearance. Found via the Brent method, λ* enables practical uses: ensuring accessibility, detecting metamerism, verifying safety colors, and revealing forgery. It’s a foundation for making color trustworthy across industries.

📇 ARBE λ* Atlas – GPT Cards

🟦 Card 1 – ARBE λ*: Brent Calculator

Discover the balance point of light. This GPT calculates ARBE λ* – the exact wavelength where absorbed and reflected energy are equal – using the robust Brent method.

What you can do:

  • Try with a flat spectrum (λ* ≈ 555 nm)

  • Upload your own spectrum data

  • Learn why λ* is a fingerprint of color

🟩 Card 2 – ARBE λ*: Metamerism Checker

Two colors may look the same – but are they really?
This GPT checks whether two colors share the same spectral identity – or are metameric.

What you can do:

  • Compare two spectral reflectance curves

  • Detect if colors are metameric (visually identical, physically different)

  • Understand why λ* reveals what CIELAB sometimes hides

🟩 Card 3 – ARBE λ*: Safety Color QC

Check the reliability of warning colors. This GPT verifies if a spectrum lies inside the λ* safety window for critical safety tones.

What you can do:

  • Validate firetruck red (λ* ≈ 590 – 610 nm)

  • Test safety yellow (λ* ≈ 570 – 585 nm)

  • Learn why λ* makes safety measurable

🟨 Card 4 – ARBE λ*: Spectral Cluster Tool

Find harmonious color groups with a shared spectral identity.
This GPT clusters colors from the ARBE λ* Atlas according to their spectral balance wavelength and creates harmonized palettes.

What you can do:

  • 🎯 Cluster HLC colors with similar ARBE λ* (± Δλ)

  • 🎨 Create palettes with spectral coherence

  • 🧠 Understand how λ* proximity supports harmonious feeling

  • 🗂️ Export the clusters as JSON, CSS tokens or PNG swatches

🟨 Card 5 – ARBE λ*: Accessibility Contrast

Keep interfaces readable across lighting. This GPT builds AA/AAA text–background pairs from the ARBE* Atlas and controls λ* separation so colors remain stable beyond a single display profile.

What you can do:

  • ♿ Build AA/AAA pairs with WCAG targets

  • ↔️ Set λ* proximity thresholds (e.g., ≥ 25 nm)

  • 🧭 Snap any HEX/Lab to official Atlas samples (Hybrid: Sample · HEX · Lab · λ*_V2)

  • 📦 Export as JSON tokens, CSS variables, or PNG swatches