The Gammatec GD-1A and GD-2 are lightweight, easy to use, portable densitometers for measuring the transmission density of x-ray film. The operator simply zeroes the instrument on the viewer, places the film on the viewer, places the probe on the area of interest and reads the density on the 3 digit LCD screen. The units have been designed for use in on-site mobile darkrooms, laboratories and offices. The GD-1A has a cable and pencil type probe, whilst the GD-2 has a built-in probe.