Show HN: Transforming an iPhone and a $20 Smart Plug into an f-stop Timer

Darkplug, created by Péter Szentkirályi, is a specialized iOS application that converts your iPhone into a professional darkroom timer capable of controlling your enlarger via a smart plug.

Core Purpose: Provide film photographers and darkroom enthusiasts with a high-precision timing tool that integrates guided workflows with a hardware-safe interface.

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🔴 Engineered for the Darkroom

Darkplug isn't just a stopwatch; it is a dedicated tool for the printing process. It replaces clunky, outdated analog timers with a streamlined digital experience.

Visual Safety & Design

The app utilizes a specific red-on-black color palette. This is critical because the red hue was rigorously tested to ensure it does not fog light-sensitive photo paper. The interface is:

• High-contrast for visibility in dim environments.
• Intuitive, keeping the focus entirely on the exposure.
• Safe, allowing the device to sit directly beside the enlarger.

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🛠️ Functional Capabilities

Whether you are performing a simple exposure or a complex multi-stage print, Darkplug handles the logic.

Standard Features

• Straight Printing: Simple, precise timing for single exposures.
• Pre-exposure: Includes an optional 4-second count-in to prepare the paper.

Darkplug+ (Premium Features)

For those requiring professional-grade control, Darkplug+ unlocks a suite of advanced tools:

1. F-Stop Integration: Adjust your timer using standard f-stop increments.
   • Math Note: Exposure time changes follow the inverse square law, where the relationship between stops is represented as: $\text{New Time} = \text{Old Time} \times 2^n$ (where $n$ is the number of stops).
2. Guided Test Strips: Execute test strips using either second-based or f-stop-based increments.
3. Dodge & Burn Grid: A unique, easy-to-navigate grid system for planning complex masking sequences.
4. Plan Persistence: (Coming Soon) Save your dodge and burn configurations via reusable plan codes.
5. Split Grade Timing: A two-channel timer specifically for split-grade printing.
6. Developing Timer: A guided assistant for the paper development stage.

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⚙️ Technical Implementation

How it Works

The app communicates with your hardware over your local area network (LAN).

Setup Checklist

• Install a compatible Shelly smart plug.
• Connect the plug to your local Wi-Fi.
• Identify the local IP address of the plug (e.g., 192.168.1.50).
• Ensure your iOS device is on the same network.
• Enter the IP into Darkplug to establish control.

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🔌 Hardware Compatibility

Darkplug is designed to work specifically with Shelly brand smart plugs. The following models are supported:

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🖼️ The Result

By combining affordable smart home hardware with a specialized software interface, you can achieve professional results:

Support & Legal

• Contact: For feedback or technical assistance, reach out via email at fill.cans82@icloud.com.
• Privacy: Please refer to the official Privacy Policy for details on data handling.