I took some comparison photos last night through my Armasight NYX-14 Gen 2+ HD and recently acquired ENVIS 703e. The tube in the Armasight is an Ekran EPM 215g-11-26AR with a photocathode sensitivity of 530 uA/lm, 66 lp/mm resolution and 25.4 SNR. Others would know better than me, but I believe the ENVIS has a Gen 3 MX10160A tube with roughly OMNI IV or V performance.

I took the photos at my house which is in the city and not very dark. My street has street lights so the pictures taken from my front yard are under fairly bright conditions. My backyard is much darker since it is surrounded by tall trees. The camera I used is a Nikon D3200. Pictures were taken using a tripod and I used different exposure settings depending on the amount of available light, but the settings were exactly the same for both monoculars on each pair of pictures.

I will update this thread with more pictures under darker conditions next time I have a chance to get away from the city.

NYX-14 on the left, ENVIS on the right.






The conditions were actually very dark in this picture. Taken with a four second exposure:

What effect does the device's lens have on the overall brightness and clarity of the imagine?

I don't really know anything about optics so I'm sure others could answer that a lot better than I could. I think both monoculars use f 1.2 objective lenses. I've read that the ENVIS is supposed to have really good optics, but don't know specifically why. From a practical standpoint, the diameter of the ocular lens makes a big difference for me. I noticed that the eyepiece lens on the ENVIS is a little bit bigger than the lens on the NYX-14, but they are both very useable. I've looked through a few scopes with tiny ocular lenses and it made me never want to use them again.

Very nice comparison images. Obviously, the Gen 3 is brighter (surprise, lol), but your Gen 2 tube looks pretty decent. Only you can say if the Gen 2 meets your requirements. In the 4th and 5th envis shots there are some streaks. Any idea what those are from? Looks almost like a streak on the front lens.

A great thanks for someone finally posting comparison pictures side by side!
Great looking back yard and pool.
I am up for adoption and would clean the pool for free. :)

That is a pretty nice Gen 2+ tube.

Those streaks seem to be in all of the Gen3 pictures. Look closely and you can see them, only in different orientations in each picture.

That is a very good Gen 2 tube.  The difference that I have seen first hand are much more noticeable.  

one of the dangers of using them in the city.  Looks to be light streaks to me.

ask me how I know

The streaks are most often called phosphor persistence (not really correct) but are really just a temporary depletion in the photocathode due to high light. Some tubes show this more than others. It is caused by panning the scope across bright lights. You can see in his photos that the streaks are in some pics but not all of them. They disappear quickly once you move the scope away from the bright light that caused it. Newer autogated tubes don't show this as much. The Envis tube he is using is not autogated. The streaks don't hurt the scope at all.

In a high light environment such as when these photos were taken Gen 2 and 3 look very similar. It is only when you take them to a very dark environment with no city light pollution that you really see the difference. Nice job OP !  I would like to see this side by side done in a dark setting. You have excellent camera skills and your photos are very good ! Actually, I would rather have a good DEP or US Gen 2 in urban areas if I did not have access to autogated tubes.

Cj7Hawk wrote a technical post on the streak effect which I will share below. It is kind of technical and I just gave you the simple answer about the streaks.

Hi Guys,

There's a few red-herrings in the above discussion, and a few mis-assumptions on all parts by all parties. Stanley's correct about the ideas getting close, but everyone, Stanley included seems to have missed the smoking gun here.

Normally, I'd just write up an article on the effect, but give the extent to which this is misunderstood, I'll go right through it, including looking at what needs to be considered and how to collect the evidence necessary to reach a conclusion, since it's an interesting topic.

Problem: Black "hair-like" lines are appearing in my image intensifier when I pan past a bright light.

Hypothesis ( provided by Stanley ) : That this is due to saturation in the Microchannel plate.
Supporting evidence : Comments on L3 vs ITT - Mention of the MCP and the L/D of the plates. ( L/D of L3 MCPs tends to be higher than with ITT MCPs due to the narrower diameter of L3 MCPs"

Evidence and Observations.
When panning past a bright light, a thin hair-like like appears to follow in the light's wake, that can last anywhere from many seconds to several minutes.
This;
a) Is not observed with Gen2 scopes. It appears to be a Gen3 related issue.
b) Seems more prevalent on L3 tubes than ITT -but has been seen on both.
c) Does not seem to be prevalent on either ITT Pinnacles or L3 Filmless while autogating.

Clarification? What is saturation?
A: Saturation is a condition that occurs on a MCP where there are so many electrons being created within the microchannel, that it depletes the charge from the surface of the downstream channel. This tends to become self-limiting and affects the maximum amplification and current drawn by the MCP.

OK, well, the first screaming clue he is that the Gen2 monoculars don't exhibit hair trails, while exhibiting all other symptoms of depletion modes of operation.

But if we ignore that, the question is “How long should it take a MCP to recover from saturation? Well, we could conduct experiments, or we could expose our shiny new tubes to daylight... OK, I will cheat. I will just look up someone else's research.

http://ist-socrates.berkeley.edu/~fajan ... NNPRSI.PDF

OK, those guys are slamming electron plasma into the MCP! Harsh!. You can read the entire document, but the graph you want is the last one. It shows the charge time of the MCP after the entire MCP suffers electron depletion. The time scale there is about 1 millisecond, which is limiting them from using a high speed camera and fast multiple events.

Simple version: The MCP channel depletion can be recorrected in about 1 millisecond – less than the decay time of the phosphors we use.

So given that MCP depletion can be corrected by normal circumstances and that the level of incomming electrons is not all that high under normal use, what else might the cause be?

And now we come back to the difference between Gen2 PCs and Gen3 PCs. Gen2 Photocathodes are simple. Gen3 aren't that complex either, but work differently.

Anyway, A typical Gen2 photocathode ( Multi-alkali metal ) is around 1200A ( A for Angstrom, since I can't make the A with a circle above it easily ) or around 120nm – quite short – not even the wavelength of blue light...

A Gen3 photocathode is around 1.0 to 1.8 micron ( 10000A to 18000A ) for the active layer. Perhaps even more. Way thicker than a Gen2.

They can't make Gen2's that thick, because electrons won't make it far enough from the atoms to the vacuum band – but in Gen3, because of the negative electron affinity, the electrons make it all the way to the vacuum band no matter where they come from. That's why they can make them thicker, which means they catch more light. This is a lot of the reason that Gen3 photocathodes are so much better than Gen2's when it comes to sensitivity.

OK, there's one more clue.

Due to the large number of electrons in the conduction band in metal, this means that electrostatic fields don't penetrate very far into metals.

On the other hand, because of the smaller number of electrons in the conduction band of semiconductors, electrostatic fields penetrate a LONG way into semiconductors.

One final thing. GaAs? It's a semiconductor.

Now we know photocathodes are subjected to HUGE electrostatic fields. Something on the order of several thousand volts per millimeter. That's a lot. And this penetrates the photocathode and causes something called band bending. It also tends to push electrons towards the MCP side of the photocathode.

But a Gen3 photocathode uses the entire thickness to catch photons right?

So that means that the electrons from the power supply that are needed to fill the electron holes in the photocathode are drawn towards the edge nearest the MCP and are slow to fill the holes further away. Singe the photocathode sensitivity across the entire thickness is roughly linear, that means that if you hit the photocathode with a really bright light, that's really thin as it moves across the photocathode, then

a) there's not much electrostatic field generated there to pull electrons to the electron holes.
b) There a very localised dip in sensitivity caused by electron depletion and too many electron holes.
c) The PSU is generating a HUGE electrostatic field in the other direction, drawing electrons away from it.
d) It tends not to fill in while the PSU is on.

OK, now that seems to explain the black hairline trails pretty well. It's like a bucket of Yoghurt. Draw a spoon head through it, and it fills in the hole and loses it's intensity. Draw a spoon handle through it and you get a clean line that fills in very slowly. Try it next time you're eating yoghurt. Depends on the yoghurt. No fruits.

OK, final clue – Doesn't occur when autogating.

So what does autogating do. It reverses the electrostatic field at the photocathode. Reverses. So all those electrons near the MCP are pushed away to the other side of the photocathode... Where all the electron holes are waiting.

Simple eh?

Anyway, I think this phenomena describes what is being seen when you pan past a bright light and it leaves spider-web trails of thin black lines in your view.

Regards
David

Thanks guys. The streak is actually present in all of the pictures. It's just harder to see depending on what background it is sitting on. Based on my brief inspection, it seems to be caused by a very light scratch/imperfection in the glass on the input side of the tube. I have however, become well acquainted with the bright-light streaking that you guys have referenced. That's certainly an interesting difference between Gen 2 and Gen 3 tubes that I wasn't previously aware of. It seems like pretty much any light source, no matter how big or small will cause streaks on the Gen 3 tube, as opposed to the Gen 2 tube, which doesn't seem to get them at all.

I can just imagine what the ENVIS would look like if I tried to do this with it


I'm definitely going to try to get some pictures in a darker setting. I go and attempt to shoot hogs about once a month so hopefully I won't have to resort to taking dark pictures in my hallway bathroom. By next week, I should also have a filmless autogated PVS-14 to compare, assuming I didn't fall victim to an ebay scam.

Thanks! I'm just using my Nikon D3200 with a tripod and holding the monocular up to the lens with my hand. I tried using the camera adapter that Armasight sells, but it didn't hold the monocular close enough to the camera lens. I have it set on Auto focus, ISO 100, and then I adjust the shutter speed depending on the amount of ambient light.

Nice job Rich!

It seems as though the differential in image quality increases as the available light decreases, as expected.

How are you addressing the manual versus non-manual gain?

Thanks John. Yes, the ENVIS maintains its brightness better as the ambient light decreases. One thing I noticed though that isn't apparent from the pictures is that the Gen 2 still produces a usable image under low light conditions even though it is comparatively darker than the Gen 3. I think this is where signal to noise ratio comes into play. Despite the lower sensitivity of the Gen 2, the high signal to noise ratio allows it to produce an image that looks very similar to the Gen 3 when actually viewed through the scope with dark adapted eyes.

I realize that this probably only applies to a certain extent and then eventually you reach a point where the Gen 2 simply cannot gather enough light and the Gen 3 leaves it in the dust. It does mean, however, that in real-world use the difference in performance will be narrower than the images suggest.

This concept also applies to your question about manual gain. I set the gain to max on the NYX-14 because the camera likes brightness. When I'm actually using the monocular, I prefer to back off the gain a little because it produces a cleaner image. Reducing the gain also results in better pictures, but it requires that I increase the exposure time in order to compensate for the decrease in brightness. Since I wanted to maintain identical camera settings for the comparison, I had to leave the gain on max so it would be similar in brightness to the ENVIS.

Here's some pretty good stuff on Signal-to-Noise Ratio off the Photonis website:

http://www.photonis.com/en/content/105-nightvision-signal-to-noise-ratio

Pretty much all good thoughts.

I think it is entirely appropriate for this comparison that you do not manually manipulate the gain on one device so as to "artificially" skew image quality.  It also appears as though you are doing your best to keep both NODs in focus; there is some history where others have posted "comparison" images where one of the devices was clearly out of focus, intentionally or otherwise.

The image pairs that I find most interesting are #2 and #3.  I don't know if the term "shadows" is correct, but when looking to the right side of the house in #2, and more importantly on the porch, there is a clear difference if there might happen to be a "subject of interest" in either of those areas.  The same holds true for both sides of the shed in #3.  When you get away from the city lights, those "shadows" will be the world if under canopy.

I don't know that SNR is really the dominant parameter for the environment that you were in as there are no indications of scintillation, even with the manual gain on max.  PCR is probably why the images appear darker, as there is only so much that the device can do with the available light.

Now please bear in mind that I am not a rocket surgeon like some of the other folks here, but simply an aging engineer who has enjoyed experiencing green glow in the dark for a while.  Also, we are relying on your firsthand observations, which are arguably better interpretations of the real image quality versus that which can be captured photographically.  Please keep the data coming

Pretty much the bottom line. Still, this Gen 2 unit could work for some uses/budgets on brighter nights. It is a very clean looking tube. It is nice to have the option in the marketplace. Not everyone can afford Gen 3. To those that can, Gen 3 is certainly the way to go.

Found some good deals on a few Gen 3 PVS-14's on ebay last week. I took some more comparison photos last night and also snapped a few pictures while hog hunting this weekend.

Here are the contenders: (From left to right)

L3 Filmless, ITT SELA with 04' date code, AEO L3


L3 11769UG-NA-C001-18UM:


KM272864-8 DC0423 S/N 789234:


AEO L3 Autogated:


Some notes:
- None of these units came with data sheets so I don't know the specs of each tube.
- I sold my Gen 2 unit to a friend, so I wasn't able to include it in the comparison, but since the pictures were taken in the same general area you can still get an idea of the relative performance.
- It is becoming more and more apparent that if you live in or near a city, extremely dark outdoor conditions are not very common. The only place I have been able to make any of these units break a sweat is indoors.

Filmless:


ITT SELA:


AEO L3:


Filmless:


ITT SELA:


AEO L3


Filmless:


ITT SELA:


AEO L3:


Filmless:


ITT SELA:


AEO L3:


Filmless:


ITT SELA:



AEO L3:


Filmless:


ITT SELA:


AEO L3:


Below are are some pictures I took with the filmless unit while we were hog hunting this weekend. There was about a quarter moon, with high clouds. The property is located about 15 miles outside of the city so there is a fair amount of sky glow along the horizon. There was also quite a bit of illumination from the moon since we were in an open field. Despite the relatively high ambient light levels, the visibility was very poor due to dense fog and high humidity.

Great pics yet again.  Urban environments have their own unique challenges despite the perception of plenty available ambient light.

"Who knows what evil lurks in the hearts of men? The Shadow knows!"

Try putting a subject of interest in the shadows, and that will tell the difference among poor, decent, good, better, and best....like to the right side of the shed.

The contrast in those filmless pics is breathtaking. Also seems the resolution is a bit better than on the 2 other tubes, although the AEO comes pretty close. Hard to tell from images whether they are properly focused or not, but if they are the difference is much larger than I thought it would. Cool pics.

Thanks! I will see what I can do, but it may take a while to convince my wife to dress up like a burglar and stand beside our shed at 1:30 in the morning

My prediction is that all three of these units would do fairly well at this test, although I would say that if my main concern was detecting bad guys lurking in the shadows, a $350 iPhone case would probably work better than all of them

All kidding aside, I think your point is well-illustrated in the photos from inside the house:

Filmless on the left, ITT SELA on the right


Although not a huge difference, the slats on the door and the second pillow on the couch can ben seen with fairly good detail with the filmless tube, but they are pretty much black on the picture through the SELA tube. One thing to note is that these differences are less pronounced when actually looking through the tube as opposed to looking at the photos.

The main thing I noticed about the filmless tube in comparison to the thin-film tubes is the contrast. The contrast of the the filmless tube is amazing. Everything looks exceptionally sharp and crisp compared to the somewhat softer image of the thin-filmed tubes. To a lesser extent, I can also see a difference in contrast between the AEO tube and the ITT tube. The analogy that keeps coming to mind when comparing the the ITT tube to the L3 tubes (especially the filmless) is the difference between LCD and Plasma TV's. At first glance, the brighter screen on the LCD seems more impressive compared to the dimmer looking plasma screen, but after a while you start to notice all those inky blacks and the shadow detail of the plasma, and you soon grow tired of the blindingly bright LCD screen that used to seem so appealing.

A couple other things:
- As I believe I had read here before, the filmless tube exhibits more ion strikes than the filmed tubes. It doesn't show up as much in these longer exposure pictures, but is easily observable when I take a quick snapshot with my phone:


- The whining sound of the autogated power-supply sounds much louder to me under low-light conditions than when it is exposed to light. From what I've read, I thought it was supposed to be the other way around. I wonder if this is because the thicker MCP of the filmless tube has a different resonant frequency or maybe it has something to do with the fact that I can't hear anything over 16khz.

Excellent comparison post OP!
Thank you

You're absolutely right about the contrast. It really is as impressive as it looks in the pictures. I tried my best to make sure each unit was properly focused for every picture. I think the main variable was how still I was able to hold the scope for each shot. I usually take multiple pictures for each scene to insure that I get a good picture, but this time I only took one of each in the same order because I was worried I wouldn't be able to tell which was which when it came time to review them. With that said, I feel like was able to remain fairly steady-handed and the results seem consistent from group to group.



Thanks!

Great job, thank you so much.  The filmless is breathtaking!  I suspect that the filmless has a higher lpm.

Lets be real, all three are beautiful tubes.  

I was more alluding to the Gen2 versus Gen3 images as far as the shadows in an urban environment.

Rich!!!!  
I bought another pvs14 because of you!!  

I made a video comparing the filmless tubes I have with my other Gen 3 tubes. The video was taken in the darkest room of my house (the hallway bathroom). I closed the bathroom door and all the other doors in the hallway. The camera was on a tripod 3 feet from the USAF resolution chart.

The only source of light for the videos was the LCD screen and green LED on the back of the camera. For each tube, I took part of the video with my thumb covering the green LED and part with it uncovered. The brighter scenes are first and the darker scenes second.

Tube information and high light resolution pictures are also posted below:



L3 M890-AV (Filmless MX-10160)



L3 11769UG (Filmless MX-11769)



L3 AEO (Thin Film Autogated)



ITT OMNI IV (Standard Film Non-gated MX-11769



ITT Select Alpha (Thin Film Non-gated MX-11769)

I like the OMNI IV, just like in real life.  

Yea it's a nice tube. Holds it's own vs. the other tubes despite being 10+ years older than some of the newer ones. Hard to go wrong with any Gen 3 OMNI IV and up.

I have five devices with tubes, three are high spec Pinnacle, one is L3 OMNI VII, and the other is an old ITT OMNI IV.  If I could only have one of them, it would be the OMNI IV.....it just seems to be the most pleasing to my eye, regardless of being "lower spec".

Here are a few pictures I took with the OMNI IV:







Taken with iPhone: