Spectral Imaging Method for Transmissive Media

An imaging process is described which captures spectral transmittance for transmissive media. The specific application is positive and negative large-format film. The system is based on a ten channel LED backlight source and a monochrome camera. The LED source sequentially back-illuminated reference targets and film samples, with an image captured for each LED channel. From the measured data and images of reference targets, a model was developed to predict spectral transmittance. With that model, the 10 images of a sample were combined to a single 31-band spectral image. Spectral images can be used to calculate colorimetric data for each pixel. These colorimetric results show that the system produces good colorimetric predictions when compared to the most relevant FADGI guidelines. Some improvement is required for the spectral model particularly in the red region.