NegPy

NegPy turns scans of film negatives and slides into finished pictures. I wrote it because I wanted a tool made for film scans that does more than invert them. It models film and photographic paper, and adds the conveniences of a lab scanner on top.

It is written in Python and runs on Linux, macOS and Windows.

The User Guide covers every panel and control. The same text opens inside the app from the ⓘ on each panel. PIPELINE.md explains the math.

• No camera profiles and no border color picking. The orange mask is removed from each channel's own sensitometry.
• The print is built in density space on an H&D curve with a toe, a straight section and a shoulder, and graded in ISO-R points like darkroom paper.
• Auto Density and Auto Grade meter each frame, so a conversion is usable before you touch a slider. You can set your own targets.
• Paper profiles taken from Ilford, Kodak, Foma and Fuji datasheets.
• Color negative, B&W and slide modes. Slides open as captured, with optional normalization for faded film and HDR merging of bracketed exposures.

• The library is a list of rolls. A roll is a folder you import, or a virtual roll you build from any frames.
• Roll-wide defaults for film mode, crop, calibration, metering, raw decode, lens and metadata. A frame you change stays yours until you push the roll setting back to it.
• Roll Analysis measures the whole roll and gives every frame the same baseline. Scenes split a roll into groups that each get their own.
• Keep/reject triage, half-frame splitting, stitching of multi-shot scans, and search by metadata or (opt-in) by what is in the picture.

• Film scanners: Plustek OpticFilm 8200i SE and 8100 V2 over USB, Nikon Coolscan through its own driver, Reflecta and Pacific Image, and anything SANE supports.
• Tethered camera scanning, including red/green/blue narrowband captures with an RGB Scanlight. macOS and Linux only. See the Camera Scanning guide.
• Trichrome merge of three narrowband exposures, with sub-pixel alignment.
• Flat-field correction, sensor calibration for narrowband light, and lens correction read from the file.
• Camera RAWs, TIFF, DNG, JPEG XL and scanner formats such as Pakon, Coolscan NEF, Flextight FFF and Noritsu.

• Dodge and burn with polygon, oval and card-edge masks. Each mask has its own strength, feather, contrast grade and tone limit.
• Dust, hair and scratch removal: automatic, from the scanner's IR channel (NegPy or OpenICE method), or painted by hand. Heals keep the film grain.
• Darkroom tools: test strips, a color ring-around, a step wedge, a zone overlay, a spot densitometer and zone placement.
• Contrast mask, tilt and swing, edge burn, filed carrier and print mats.
• Lith and cyanotype processes and a set of toners for B&W.
• GPU rendering through Vulkan, Metal or DX12, with a CPU fallback that gives the same result.

• ICC color management with monitor profile detection and soft proofing for paper and printer profiles.
• Export to JPEG, TIFF, PNG, WebP and JPEG XL, with borders, presets, contact sheets and filename templates.
• A flat 16-bit TIFF master for Lightroom, Darktable or Photoshop, or a linear export that skips the pipeline.
• Gear and capture metadata (camera, lens, film, development, date and place) written to EXIF and XMP.

• Non-destructive. Source files are never modified.
• Edits live in a local SQLite database keyed by file content, so you can move and rename files. Optional .negpy sidecars sit next to the scans.
• Undo history and named work prints survive a restart.
• Keyboard shortcuts can be remapped.

Download the build for your OS from the Releases page. After that, NegPy updates itself: when a new release is out it shows an Update Available notice, and one click downloads and installs it.

To build from source, see CONTRIBUTING.md.

The builds are not signed. It is a free hobby project and I don't pay Apple or Microsoft for developer certificates, so expect a warning the first time you run it.

Make the .AppImage executable with chmod +x and run it.

Scanning through SANE needs SANE installed. Tethered camera scanning may need libgphoto2. The app runs without either.

sudo apt install libsane        # Debian/Ubuntu
sudo pacman -S sane libgphoto2  # Arch

nix run github:marcinz606/NegPy

Or add it as a flake input:

{
  inputs.negpy.url = "github:marcinz606/NegPy";
  outputs = { self, nixpkgs, negpy, ... }: {
    # negpy.packages.<system>.default
  };
}

1. Open the .dmg and drag NegPy to /Applications.
2. Run xattr -cr /Applications/NegPy.app in Terminal to clear the warning.
3. Launch it.

SANE scanning and camera scanning use Homebrew packages. The app runs without them.

brew install sane-backends libgphoto2

To build the DMG yourself, set NEGPY_MACOS_ARCH=x86_64 for Intel or NEGPY_MACOS_ARCH=arm64 for Apple Silicon.

Run the installer and click through the warnings.

Plustek OpticFilm 8200i SE and 8100 V2 scanners need the WinUSB driver. Install it with Zadig in place of the SilverFast driver (07b3:1825 for the 8200i SE, 07b3:1824 for the 8100 V2). The release build includes everything else. See PLUSTEK_WINDOWS.md. Camera scanning is not available on Windows, because libgphoto2 has no Windows build.

Everything is in Documents/NegPy. On Windows, if that folder is blocked, NegPy asks for another one and suggests Local AppData. The NEGPY_USER_DIR environment variable overrides both.

• edits.db: your edits.
• settings.db: app settings such as the last export settings.
• cache/: thumbnails. Safe to delete.
• export/: default export folder.
• icc/: paper and printer profiles.
• override.toml: startup overrides, see below.

If NegPy crashes on startup or renders wrong, edit override.toml. NegPy writes it on first run with defaults for your OS. Most [performance] values are also in Preferences (Ctrl + ,), but the file wins, so you can fix things when the app will not start.

[rendering]
# Options: "auto", "vulkan" (Linux/Win), "dx12" (Win), "metal" (macOS), "cpu"
backend = "vulkan"

[display]
# Qt scene-graph backend. Options: "auto", "vulkan", "d3d12", "metal", "opengl", "software"
qt_rhi_backend = "auto"

# Window system plugin (Linux only). Options: "auto", "xcb", "wayland"
qt_platform = "auto"

[performance]
# Cap GPU texture size in pixels — useful on low-VRAM cards. "auto" = no limit.
max_texture_size = "auto"

# Force HQ preview on/off. Uncomment to override saved preference.
# force_hq_preview = false

# Long edge of the interactive preview in pixels (512-8192). Higher is a sharper
# canvas and more VRAM per frame.
# preview_render_size = 1600

# Preview cache size — keeps recently-viewed photos in memory for instant navigation.
# Lower these on low-RAM machines. Uncomment to override defaults (~1.2 GB / 8 photos).
# preview_cache_max_bytes = 1200000000
# preview_cache_max_entries = 8

[logging]
# "debug", "info", "warning", "error"
level = "info"

backend = "cpu" turns GPU rendering off, for when the GPU backend crashes on your hardware.

• Roadmap
• Changelog
• Contributing

GPL-3.

If you like NegPy, buy me a roll of film so I have more test data :)