Under-Exposure

Allowing too little light to reach a photosensitive material. Results in a "thin" or light image with negative material and a dark or "dense" image with reversal material.

USB

Universal Serial Bus. A protocol for data transfer to and from digital devices. Many digital cameras and memory card readers connect to a computer via USB ports. USB card readers are typically faster than cameras or readers that connect to a serial port, but slower than those that connect via FireWire.

UXGA

Ultra Extended Graphics Array. 1600x1200pixels image resolution, most appropriate for big enlargements.

UV Filter

Filter used to reduce ultraviolet light exposure of film. Ultraviolet light can cause an image to appear hazy.