A portable digital image capturing and processing system comprising: an image formation and detection subsystem; a narrow-band illumination subsystem; a narrow-band transmission-type optical filter subsystem; an automatic light exposure measurement subsystem; and an automatic illumination control subsystem. The image formation and detection subsystem has an area-type image sensing array for detecting digital images of objects formed thereon by image formation optics providing a field of view (FOV) for the system. Within the FOV of the image formation and detection subsystem, the narrow-band illumination subsystem produces a field of narrow-band illumination consisting essentially of a narrow band of wavelengths of visible illumination. The narrow-band transmission-type optical filter subsystem transmits substantially only the narrow band of wavelengths of visible illumination produced from the narrow-band illumination subsystem, and rejects all other optical wavelengths outside the narrow band however generated by ambient illumination sources. The automatic light exposure measurement subsystem employs a photo-detector operated independently from the area-type image sensing array, for automatically measuring the light exposure incident upon a selected portion of the FOV, and producing an electrical signal representative of the light exposure measurement. Only when all sensor elements in the image-sensing sensing array are activated and in state of integration, then narrow-band illumination is produced for illuminating objects in FOV of the system and simultaneously detected by a photo-detector for measuring light exposure within the FOV, and also by an area-type image sensing array for detecting a digital image of said illuminated object.