NNVT vs Photonis ECHO at a Glance
NNVT (North Night Vision Technology) is a company that produces image intensifier tubes from China. Recently they have entered the Western commercial market with Gen 2 White Phosphor image tubes that are based on Photonis XD4/XR5 era technology. This provides both pros and cons compared to newer ECHO technology, which will be discussed in more detail later.
NNVT tubes are non gated whereas ECHO tubes are gated. ECHO tubes are rated 1600 FoM to 2000 FoM, whereas NNVT tubes are rated 1200 to 1600 FoM but generally average around 1400 FoM.
For our comparison, we are using Carson lenses. Fujinon OEM Carson objective, with Qioptiq OEM Carson eyepieces.
The NNVT tube is right in the middle of the line of our batch from a spec perspective. The ECHO is an above average ECHO. One thing that was notable to us was the NNVT shipment we received had very few blems, whereas clean ECHO tubes are relatively very rare. We had to hand pick a clean one for this comparison as it is a performance comparison, not a tube cosmetics comparison.
Relatively bright moon, some stars overlooking subarban homes. You will notice that the NNVT tube is slightly grainier because of the lower SNR but overall, it is a very comparable image.
Overlooking a pond, near full moon to the left outside of the field of view. Image clarity is very comparable.
Here we have a dynamic light and flare test. In this case I think the NNVT tube does better than the Photonis ECHO, as ECHO tubes are notorious for their "Rising Sun" style flare out of point light sources. Though, the ECHO does do a slightly better job of seeing past the initial orb flare. Again, these are both with the Fujinon objectives and Qioptiq eyepieces.
Another dynamic light test, but this time less direct. Streetlights down a street, you can still see the "Rising Sun" style flare from the ECHO tube. Same as before, it is much easier to see past the orb flare with ECHO than NNVT.
It is very difficult to tell from these photos, but while the ECHO has marginally better clarity in well lit areas, the NNVT tube actually has noticeably better clarity on point light sources. The reason for this is the NNVT tube is based on XD4/XR5 technology and not wide spectrum technology that ECHOs use for their photocathodes. What this means is that the NNVT is photosensitive to a much narrower band than the ECHO, which means that light focuses more evenly. While it can be advantageous to have wide band photosensitivity, it can in some cases decrease resolution due to different wavelengths focusing differently through the same lens.
If you have ever driven under NVGs, this is why green lights always look slightly out of focus compared to red lights and other street lights. Green focuses differently through most PVS-14 lenses.
In low light, the NNVT tube is brighter because it has a higher gain and higher EBI. The ECHO produces a clearer image.
Overall the NNVT tubes are quite impressive given the price point, and definitely provide an incredible value for the cost. We are very excited to begin offering NNVT tubes in our units now that we have done testing to ensure the tubes are of good quality. These units will be available at a significantly friendlier price point without the significant performance sacrifices involved in using lower quality housings and lens systems.
Stay tuned for further qualitative and quantitative comparisons for both image intensifier tubes and lens systems that we will be conducting using our Hoffman Engineering ANV-126A.