NegPy converts film scans using density-space darkroom modeling
Convert scanned negatives and slides with density-space film and paper simulation, orange-mask neutralization, and roll-based batch normalization. NegPy, created by marcinz606, targets photographers and archivists needing precise film-to-positive conversion on Windows. Key processing steps include H&D curve modeling, automated mask removal, IR-based dust repair, and RAW/HDR support. The app fits users who scan film regularly and require granular control over density, contrast, and color balance for consistent, print-ready results.
How accurate is the film-to-positive conversion?
NegPy models film and paper response in density space rather than applying a simple RGB inversion, which reproduces darkroom characteristic curves for color fidelity. The tool includes built-in paper profiles derived from Ilford, Kodak, and Fuji datasheets, and offers per-channel H&D curve controls. These elements let the app mimic physical sensitometry and produce conversions that reflect film behavior across exposure and contrast ranges.
Does it affect system performance during processing?
Processing relies on Python libraries such as OpenCV and NumPy, and on Windows it’s typically distributed as a standalone executable to avoid manual environment setup. The workflow can run batch normalization across rolls, which implies heavier CPU and memory usage during HDR merging or trichrome alignment. Expect longer runtimes for bracketed HDR merges and IR-based dust removal compared with single-image fast inversion methods.
Is it safe to use on archive or original scans?
The app stores processing history separately and never overwrites originals, implementing non-destructive edits saved in a local database. Automated orange-mask neutralization and mathematical normalization operate without manual border picking, reducing the risk of accidental pixel edits. The processing pipeline is open-source and documented, so the steps applied to each file are inspectable and reproducible.
Do I need technical knowledge to operate it effectively?
NegPy exposes advanced controls that require domain knowledge, including density adjustments, dodge and burn masks, and crosstalk correction for IR layers. The roll-based workflow and trichrome alignment favor users comfortable with film workflows or willing to learn technical terms. Direct scanner tethering on Windows is limited by driver standards, so users expecting full scanner control should plan for manual import of scan files.
NegPy suits technically minded film scanners who accept a learning curve
The tool delivers reproducible, darkroom-style conversions and preserves originals via non-destructive history storage. It requires familiarity with film terms and heavier processing for batch HDR or infrared repairs, so it best serves analog enthusiasts, lab technicians, and archivists prepared to manage Python-backed dependencies and longer runtimes.
