Flash Guide

A flash exposure calculator for film photographers. Calculate optimal flash distances based on guide numbers, ISO values, and aperture settings.

Features

• Dual Calculation Modes

  • ISO Mode: Calculate flash distances across multiple ISO values
  • Power Mode: Calculate distances for different flash power settings at a fixed ISO

• Interactive Interface

  • Real-time calculations with customizable f-stop ranges
  • Support for full, half, and third stop increments
  • Quick ISO preset buttons for common film speeds

• Data Visualization

  • Tabular view with copy-to-clipboard functionality
  • Interactive line charts showing distance relationships
  • Print-friendly output

• Unit Support

  • Calculate in meters or feet
  • Automatic unit conversion

Getting Started

Prerequisites

• Node.js 18+
• pnpm (recommended) or npm

Installation

# Clone the repository
git clone https://github.com/yourusername/flash-guide.git
cd flash-guide

# Install dependencies
pnpm install

# Start development server
pnpm run dev

Open http://localhost:3000 to view the app.

Build for Production

pnpm run build
pnpm run start

How It Works

Flash Guide uses the standard flash guide number formula to calculate optimal distances:

• Base Formula: Distance = Guide Number / F-stop
• ISO Adjustment: Adjusted GN = GN × √(ISO/100)
• Power Adjustment: Adjusted GN = GN × √(1/power_ratio)

Guide Number

The guide number (GN) is a standardized measurement of a flash unit's power output at ISO 100. Common guide numbers:

• Small built-in flash: GN 12-20
• Compact external flash: GN 20-36
• Professional flash: GN 36-60+

Usage

1. Enter your flash's guide number (at ISO 100)
2. Select calculation mode:
   • ISO mode: Enter comma-separated ISO values (e.g., 100, 200, 400, 800)
   • Power mode: Select a fixed ISO and view distances at different power ratios
3. Set your f-stop range using the min/max controls
4. Choose your preferred units (meters or feet)
5. Click "Calculate Flash Distances" to generate results

The results show the maximum effective flash distance for proper exposure at each combination of settings.

Tech Stack

• Next.js 15 - React framework with App Router
• TypeScript - Type-safe development
• Tailwind CSS - Utility-first styling
• shadcn/ui - High-quality UI components
• Recharts - Data visualization

Project Structure

flash-guide/
├── app/
│   ├── api/
│   │   ├── iso/         # ISO-based calculations
│   │   └── power/       # Power-based calculations
│   ├── page.tsx         # Main application UI
│   └── layout.tsx       # Root layout
├── components/
│   ├── flash-table.tsx  # Results table component
│   ├── flash-chart.tsx  # Results chart component
│   └── ui/              # Reusable UI components
└── public/              # Static assets

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is open source and available under the MIT License.