Gen. III differs from the Gen. II+ in use of a photo cathode based on Gallium Arsenate with even deeper sensitivity in the IR spectrum. The photo cathode sensitivity is 900–1600 mA/lm, resolution is 32–64 lp/mm and capacity for work is 10,000 hours.
This is 3 times longer than with the Gen. II tube. The NV units using the Gen. III tubes work very well in the low light environment. The image comes out clean and with excellent contrast. The only drawback of Gen. III units is their vulnerability to the side light distortions due to lack of the fiber optical plate on the front of the tube. Until recently Gen. II+ and III units where used mostly by the military, these units became more widely available not long ago.