much less power consumption than digital
newer ones still generally have higher resolution than current digital ones
II tube has less life span and efficiency falls over time - perhaps 5-10yrs
II tube will be destroyed if exposed to daylight
generally cannot use IR illuminators above 850nm (ie animals will see it)
lower end models are more sensitive to rifle recoil than digital
cannot record stills or videos
give monochrome green images (except for those with White Phosphor Technology (2QS and 3G) which give gray scale images)
Gen 0 - those developed prior to end of WWII
Gen 1 - those developed by US army for the Vietnam war and used a S-20 photocathode, their image intensifiers produced a light amplification of around 1000 but still require at least moonlight or IR illuminator (usually around 790nm)
Gen 2 - developed in the 1970's with improved image-intensifier tube using micro-channel plate (MCP) with an S-25 photocathode, which gave light amplification of around 20000, improving resolution and reliability; Useful range is generally up to 200m; Life expectancy is about 5,000 hours of use;
Gen 3 - developed in the late 1980's used MCP but now with used a photocathode made with gallium arsenide, light amplification is also improved to around 30000–50000, but required more power and had large halo effect; Sufficiently efficient not not require an IR illuminator or moonlight; Useful range is generally up to 300m; Life expectancy is over 10,000 hours of use;
Gen 3+ “3AG” “Gen IV” - developed in the 2000s with autogated tubes