Multi-spectral Scanning for Analogue Film Digitisation: Addressing LED Variability in Spectral Band Selection

The digitisation of analogue film is critical for cultural heritage preservation, as film deteriorates over time due to environmental factors and analogue projectors are becoming obsolete. Conventional RGB scanning methods fail to fully capture the spectral complexity of film, making multispectral imaging (MSI) a feasible alternative. However, MSI faces challenges due to the limited availability of narrow-band LEDs in certain spectral regions and inherent variability in LED emissions. Aiming to minimise colour reproduction errors in film scanning, this study investigates the optimisation of LED spectral band selection and the impact of LED spectra variability. Informed by the optimised bands, multiple market-based LED sets were further evaluated using MSI capture simulations, with the 7-band and 8-band setups achieving good colour accuracy and showing rather low sensitivity to LED spectral variability. A physical multispectral capture of a film photograph demonstrated a good agreement between the capture simulation and the real results.