Free Luminous Flux (Lumens) to Candela (Steradian) Calculator

Overview

A high-performance, single-file browser utility that allows users to convert luminous flux (measured in lumens) to luminous intensity (measured in candela). The application is designed to be a frictionless tool for lighting designers, electrical engineers, and students to calculate light intensity based on beam spread or solid angle.

Technical Implementation Strategy

• Architecture: Single HTML5 file containing internal CSS and JavaScript.
• Dependencies: Tailwind CSS via CDN for rapid styling; Lucide icons via CDN for visual feedback.
• Constraints Compliance:
  • No Storage: No use of localStorage, sessionStorage, or cookies. All calculations occur in-memory.
  • No Popups: Error handling and notifications utilize custom UI modal components.
  • Sandboxed: Designed for compatibility with null-origin iframes.
• State Management: Simple reactive object updated via DOM event listeners (input validation, calculation trigger).

Feature Set

• Dual-Mode Calculation:
  • Solid Angle Mode: Input lumens and steradians.
  • Beam Angle Mode: Input lumens and beam angle (degrees), with automated conversion to steradians.
• Real-Time Calculation: Instant result updates upon field input without requiring a 'submit' button.
• Precision Control: Floating-point precision for scientific accuracy.
• Comparison Reference: Dynamic labels showing how the calculated candela compares to a standard candle (1 cd).
• Responsive Interface: Adaptive card-based layout that centers on desktop and stacks vertically on mobile devices.

UI/UX Specification

• Header: Clean, centered title with a short, punchy sub-headline.
• Main Content: A white, shadowed "glassmorphism" card with a soft drop shadow.
• Inputs: Large, clear numeric input fields with high-contrast labels and placeholder text.
• Result Section: Large, prominent typography for the output, highlighted with a vibrant color (e.g., #4F46E5) to ensure clarity.
• Transitions: Smooth fade-in/out effects on numerical updates using CSS transition: opacity 0.2s ease-in-out.

Color Palette (Light Mode Only)

• Background: #F9FAFB (Cool Gray 50)
• Card Surface: #FFFFFF
• Primary Action/Accent: #4F46E5 (Indigo 600)
• Text Primary: #111827 (Gray 900)
• Text Secondary: #6B7280 (Gray 500)
• Borders: #E5E7EB (Gray 200)

Developer Instructions

1. Use Tailwind CSS via CDN for styling to maintain a modern SaaS aesthetic.
2. Ensure all inputs validate for non-negative numbers; display an inline warning message (not an alert) if negative values or text are entered.
3. The app must render correctly on both desktop (centered container) and mobile (full-width with padding).
4. Use clean, semantic HTML5 elements (<header>, <main>, <section>, <article>).
5. JavaScript must be strictly vanilla; no external libraries except authorized CDNs.
6. No branding: Do not include logos or specific product names.