Effect of microbial contamination of black and white photographic negative films on developed photos
摘要
Black & white (B&W) photographic negative films hold valuable historical and cultural information, making them an integral part of our cultural heritage and a significant focus for preservation institutions. However, the organic components of these films are susceptible to contamination by microorganisms, such as bacteria and fungi, which pose serious threats to the safety of the negatives and the integrity of their recorded images. This study reveals that microbial growth on the surface of B&W photographic negative films results in increased surface roughness, leading to the appearance of white patches on developed images and causing decreased image quality. To assess the effects of microbial contamination, the surface roughness and morphology of the contaminated negative films were observed using the laser microscopy system. Additionally, changes in light reflectance and transmittance were evaluated for model high-density and low-density samples of contaminated B&W photographic negative films using the UV-VIS spectrometer. The findings show that microbial contamination significantly increases the surface roughness and visible light reflectance of the negative films. The transmittance of low-density samples was markedly reduced, whereas high-density samples exhibited minimal changes. Our results indicate that reduced visible light transmission affects the grey level of developed B&W photos. Insufficient exposure of the silver halide in the emulsion layer of the photographic paper reduces silver particle formation, contributing to lower image quality. Based on these findings, we propose that microbial contamination causes surface roughness in negative films and adversely impacts the quality of developed images. This research provides a foundation for improved strategies to mitigate microbial damage and restore contaminated photographic materials in the future.