The image intensifier tube is the most important component of the night vision devices. Below is a list of currently produced tube types and manufacturers who offer them.
Gen 2+ / hybrid - Photonis and NNVT
The most affordable option. Current production Gen 2+ tubes' performance has improved significantly, reaching Gen-3 levels of resolution and SNR, although they still tend to have around half the gain, limiting their low-light performance. Expected lifespan has also improved to Gen-3 levels
The Photonis ECHO and 4G lines of tubes feature ultra-fast autogating, leading to higher resolution in high-light environments when compared to other autogated or nongated tubes.
Gen 3 thin-filmed - Elbit and L3Harris
Great cost to performance ratio. Greatly improved from early thick-filmed Gen-3 tubes. Enables night vision capabilities without the use of IR illumination in almost all field environments.
Gen 3 unfilmed - L3Harris
Unfilmed tubes on average have higher specs than thin-filmed tubes. Compared to thin-filmed tubes of identical specs, unfilmed tubes will have slightly improved contrast at all light levels. Unfilmed tubes are also slightly more shock resistant.
Gen 3 unfilmed Super-gain - L3Harris
Provides the greatest low-light performance. On top of the benefits of unfilmed tubes, Supergain tubes have 100,000-120,000 fL/fc gain compared to standard Gen 3 tubes with around 60,000-70,000 fL/fc gain. Giving them a lead in extremally low light environments, thereby minimizing instances of IR illumination being required.
Gen 4?
"Gen-4" has been used as marketing term by various companies for unfilmed Gen-3 or even just high spec thin-filmed Gen-3 tubes. It's not an actual generational designation used by the DOD
Field testing
We compared a tube of each type in the field. Please keep in the mind that the images captured by the camera have substantially degraded apparent image quality, due to the camera's limited dynamic range, compression etc. The image quality would appear significantly better if viewed directly by a person. Nonetheless, the difference between the images is indicative of the relative performance difference between the tube types.
The images were captured on a moonless night with clear skies. In an area with Bortle 4 (rural/suburban transition) level of light pollution.
Tube specs:
NVT #1
SNR: 23.7 / RES: 60 / EBI: 0.12* / LG: 9400** / PS: 894 / FOM: 1422
*multiply by 10 to convert to standard units **multiply by 3.14 to convert to standard units
Elbit #1
SNR: 33.7 / RES: 76 / EBI: 1.76 / LG: 68811 / PS: 2233 / FOM: 2561
L3Harris unfilmed #1
SNR: 32.1 / RES: 72 / EBI: 0.4 / LG: 63876 / PS: 1981 / FOM: 2311
L3Harris unfilmed Supergain #1
SNR: 32.2 / RES: 64 / EBI: 0.2 / LG: 105206 / PS: 2062 / FOM: 2061
location 1 - An opening in the tree cover
Location 2 - Complete tree cover
With very low ambient light the differences in performance are the most significant. Navigating on the path is still feasible with the NVT tube, although IR light will be required for detection. Using the Elbit and L3 unfilmed tubes, one can see roughly the same amount of detail. The Elbit tube with the higher gain is slightly brighter, however, while the L3 unfilmed tube has slightly better contrast and clarity. The L3 unfilmed Supergain tubes still remain quite bright and show the most details.
Location 3 - Open field, looking at a deer
Exposure and ISO was set to most accurately represent the actual image of the trees, ground, and deer. (Due to limited dynamic range of the camera, the sky gets whited out. Please disregard how the sky appears when comparing the tube images.) Note the difference in the ability to see under the tress