Torchslit (Vulpes)

iOS "Bulb + Torch" Camera for Long-Exposure Photography

What is it?

Torchslit is a camera app that lets you shoot true-feeling bulb-style long exposures on iPhone while precisely scripting the iPhone's rear LED (torch) as a timed light source—tap-to-burst, scheduled bursts, and repeatable "light scripts" you can replay.

Why?

iPhone's stock camera is missing what long-exposure people actually want:

• Bulb control: "start exposure… stop exposure" (not a fixed shutter time)
• Light control: timed bursts of light during the exposure (for light painting, selective illumination)
• Repeatability: save a lighting pattern and reproduce it

Core Concept

Two engines running together:

1. Bulb Capture Engine — Captures continuous frames and accumulates them into a single long-exposure image
2. Light Script Engine — Controls the LED: burst for X seconds, follow a timed sequence, repeat at intervals, or live tap/hold

Project Structure

Torchslit/
├── Sources/
│   ├── App/
│   │   └── TorchslitApp.swift       # App entry point
│   ├── Views/
│   │   ├── ContentView.swift        # Main camera UI
│   │   ├── CameraPreviewView.swift  # Camera preview layer
│   │   └── SettingsView.swift       # Settings sheet
│   ├── Engines/
│   │   ├── CameraManager.swift      # Central state manager
│   │   ├── BulbCaptureEngine.swift  # Frame accumulation (Metal)
│   │   └── LightScriptEngine.swift  # Torch control + timing
│   ├── Models/
│   │   ├── LightScript.swift        # Replayable lighting patterns
│   │   └── CaptureRecipe.swift      # Capture metadata
│   └── Shaders/
│       └── Accumulation.metal       # GPU blend modes
├── Resources/
└── Info.plist

MVP Features

• Bulb start/stop capture
• Manual burst (tap to fire torch)
• Duration selector (0.25s - 5s)
• Intensity slider
• Interval burst mode
• Three blend modes (Max, Additive, Average)
• Thermal state monitoring
• Save to Photos with metadata
• Recipe sidecar export

V1 Features (Later)

• Light Script editor UI
• Script presets library
• Apple Watch remote
• Live touch mode (hold = torch on)
• Dark frame subtraction
• RAW/DNG export

Building

1. Open in Xcode 15+
2. Set your development team
3. Build and run on device (torch requires real hardware)

Technical Notes

Frame Accumulation

Uses Metal compute shaders for real-time blending:

• Max: Brightest pixel wins (light trails, star trails)
• Additive: Pixels add together (classic long exposure)
• Average: Running average (water smoothing, traffic)

Torch Control

Uses AVCaptureDevice.setTorchModeOn(level:) with safety guards:

• Thermal state monitoring
• Consecutive burst limits
• Cooldown periods

Timing

Uses monotonic clock for consistent timestamps across:

• Shot start/end
• Frame ingestion
• Torch events

License

MIT