The night vision marketplace is confusing.  For someone new to the topic it can simply be overwhelming.  The best I can do is an overview, and hopefully this article gives you enough information to get you started.  I should state up front that I’ve been using night vision equipment off-and-on since the early 1990′s.  I think they’re a blast to use, but I’m not an engineer, I don’t make my living from these things, and I don’t bet my life on their performance either.  I’m just a user, and I’m trying to pass on some basic information to help others get started without making any expensive mistakes.

Image Intensification – Not Thermal

The goal is to see in the dark, or more likely if you’re reading this here on ShootingReviews, to shoot in the dark.  There are a few ways to do that:

• You can mount a flashlight to your rifle/pistol and use your eyes.  This works, and is cheap, and should be covered in any defensive shooting school, but it’s not what this article is about.
• You can mount a device on your rifle or helmet that measures how hot things are and displays that to you.  You’ve probably seen police helicopter footage that shows exactly this, and you probably know that this is a wonderful way to identify warm blooded creatures out on a cold night.  This is also not what this article is about.
• You can mount a device to your helmet or rifle that takes ambient light, amplifies it a lot, and allows you to see the world in green hues.  This is what we mean by “night vision” in this article.

 

Expectations

Night vision is a tool, and it can be incredibly useful in many situations, but it’s not a magic “see in the dark like it’s daytime” solution.

The good news is that when used properly it allows you to see, navigate, drive, and shoot in the dark.

The big weakness of current night vision technology is the restricted field of view.  Normally you have a field of view of about 100 degrees, while pretty much every night vision device on the market is going to offer you about 40 degrees.  This is restrictive.  If you’d like a demonstration then take a toilet paper roll, cut it in half, put one end up to your eye, and look through it.  I tested this, and the field of view there is almost exactly what I get out of a monocular.  Now, close the other eye (or use the second half-tube on the other eye if you want to simulate goggles) and walk around your house for a few minutes.  It’s restrictive.  If you want to remain aware of your surroundings then you’re going to be constantly scanning.  If you’re stalking an animal, then you’ll be looking at the animal, and occasionally glancing at your feet.  Oh yeah — if you focus on infinity the ground at your feet will be a blur.

You definitely need to practice and train with it if you really want it to be a useful tool.

ITAR

Something to be aware of up front: it’s illegal to export this stuff from the United States.  It turns out being able to see in the dark when your opponents can’t is a huge advantage in war, and the US Government has been cracking down a lot recently — at SHOT 2013 I wasn’t allowed to look through the latest & greatest night vision equipment because I didn’t think to bring my passport to Las Vegas.  But those were the rules that vendors were operating under after the rules were re-emphasized by friendly federal agents.

If you’re a US citizen this isn’t necessarily a big deal, but it’s something to have in the back of your mind.

Generations

This had been a long section, but I’ve decided to strip that out and link you to the relevant Wikipedia page instead.  If you want to know more, Google it.

Here’s my brief summary: better gear costs more.  More recent gear is better, generally, than older gear.  As a general rule, what most people should be doing is saving up until they can buy Gen3 or Gen3+/Gen4/Omni-VIII/whatever the newest tubes are marketed as.  Gen1 isn’t as useful as you’d think, and the money you save by going with Gen2 isn’t worth the trade-offs in performance (figure 40 lp/mm resolution vs 64 lp/mm), lifespan (from 5,000 hours MTBF with Gen2 to 10,000 hours or so for Gen3 depending on who you trust), etc.

You really want Gen3, or your use is an edge case.  The rest of this article focuses on Gen3 gear.

Possible Exception to the Gen3 Rule: Photonis

if you don’t live in the US, then you can’t buy night vision from US suppliers, which means you’re looking at European and Russian options.  One of the top options here is Photonis – reportedly they sell about 96% of their products to military buyers who also can’t buy the US stuff, and while it’s technically only Gen2 gear it performs shockingly well.  If you download their datasheet on the XR-5 tube, you’ll see that:

• Resolution is comparable to Gen3
• MTF is high.  (This is how Photonis is trying to distinguish themselves, so some of this is marketing, but MTF is a reasonable way to measure performance.)
• Signal to noise ratio is also quite good.
• Minimum life is ~ 15,000 hours.
• Halo, EBI are also good.

What you don’t see mentioned, however, is sensitivity.  If you look here you can see the specifications for the XR5 tube, and sensitivity is listed as 800 typical.  To compare, you can look at a summary of OMNI specifications for Gen3 night vision and see that this sensitivity is almost equal to OmniIV/OmniV performance after you take into account the light loss due to the ion barrier (see below).   For comparison, the average of the L3 unfilmed tubes I just received is a sensitivity of 2,435.

What this means is that Photonis tubes are comparable to or slightly better than OmniIV and OmniV tubes, which offer very good performance themselves.  The problem is that Photonis knows how well their tubes perform, and they price them pretty expensively.  If you live in the US and are a US citizen, then Gen3 is probably still going to be the way to go.  If not, then there are some nice tubes available from Photonis that will perform really well in all but the lowest light levels, but you’ll pay a pretty penny (or Euro) for them.

Components

All night vision devices you can buy are made up of two components: the tube itself, and the housing.

The Image Intensifier Tube

Most every Gen3 tube on the market is manufactured by either ITT (Excelis) or Litton (L3).  Tubes come in a bewildering variety of models which we’ll get to later, but for now let’s get a brief overview of the tube itself.  All Gen2 and later night vision tubes work as follows:

• Light in the visible and near-infrared spectrum is gathered and passed to a photocathode which translates the photons into electrons.
• These electrons then go into something called a micro-channel plate where one incoming electron might be represented by 50,000 exiting electrons.
• These electrons then head to a phosphor screen, where they hit the phosphor, which releases photons, and those photons are the things your eye actually sees at the end of the process.  Green phosphors are used because the human eye is more sensitive to green than to any other color, so your eye can pull more information from a green screen than other colors.

All of these steps are performed in a sealed unit, referred to as the “image intensifier tube” (or II tube, or I² tube.)  The one shown above is a mid-1990′s ITT tube.

After writing this I found a good video that illustrates the process.  This might make it clearer:

A Note on Ion Barriers

One of the changes that happened between Gen2 and Gen3 was the use of Gallium Arsenide (GaAs) in the photo cathode, which performed much better but also had a much shorter lifespan   Basically the MCP takes a few electrons on the input side and shoots lots of electrons out of the output side, but as part of this process it also ends up sending positively charged ions back toward the input side to impact on the photo cathode.  This reduces the life of the GaAs photo-cathode, and the fix was to insert an ion barrier (a 3 nanometer thick piece of aluminum oxide) between photo cathode and MCP to increase the life of the tube.  This worked, but it had some negative effects:

• It drops the sensitivity of the tube in half, so you get fewer photons to work with, and a dimmer/less detailed image.
• You get more of a halo effect around light sources like streetlights.
• It sucks more power.

If you want to know more, there’s a pretty detailed page here.  It’s marketing materials, but it’s well done.

Needless to say, greater performance was desired, so there have been attempts to get around the problems of the ion barriers.  Originally DoD put out requests for “Gen4″ tubes that had no ion barrier, but these didn’t live as long as desired (remember, that’s why we started using ion barriers in the first place).  While Litton was trying to solve the life-span issues, ITT came up with a thinner ion barrier that met the required Gen4 performance specifications, and eventually the no film requirement  went away (along with the “Gen4″ moniker) and ITT won that contract round with their thin-film technology.  These tubes still use an ion barrier, but as it’s one third as thick it offers serious performance improvements vs the prior designs.  This is sold as the ITT Pinnacle® tube, by the way.

Litton continued to work on how to remove the ion barrier, even after ITT received the majority of the original “Gen4″ contract.  Since that time, Litton has figured out how to nearly eliminate the positive ions shooting back out the input side of the MCP, and came up with a way to make the photocathode self-heal from the damage the remaining ions cause.  Early versions of these filmless/unfilmed tubes are rumored to be a bit too sensitive to use in weapons mounts, but the current L3 unfilmed Infinity® tubes are warrantied whether you want to use them in a weapons mount or not, and there are reportedly no lifespan issues.  They’re also being used in goggles issued to some pretty high-end military units.

This doesn’t mean it’s a “better” tube though.  It means that in the lowest light levels the unfilmed tube should perform better because all of the electrons passed by the photocathode make it to the MCP for amplification, as there isn’t a piece of aluminum oxide in the way to block low-energy electrons.  Expect unfilmed tubes to work better in the darkest conditions, and expect them to be more expensive because they’re still really difficult to make (I’ve read there is a 27% yield on these.)  In more typical environments it’s likely you won’t see much of a difference between L3 (unfilmed) Infinity and ITT (thin-film) Pinnacle.  Both should be noticeably brighter than tubes with 3nm ion barriers, however.

I’ll quote a very experienced night vision user on another forum on this issue who has a slightly different take:

outside, even under above-average light conditions, the unfilmed INFINITY tube exhibits clear advantages compared to OMEGA or ITT Pinnacle. They (unfilmed ones) are indeed not brighter than Pinnacles, as Stan says. But the details are extremely crispy, low EBI assures very rich color shades and the whole picture looks as if you added contrast in Photoshop. Besides that, you will be hard pressed to find a place outside where an INFINITY tube produces visible noise.

Housings

This is the other half of the night vision device.  For the most part these components are commodities — there will be differences between units, but in general they are interchangeable.  You can take a tube, drop it in one housing, then move it to another housing, and the performance will be the same.

With that said, there are a huge number of housing designs available on the market.  These differ in all sorts of ways.  Broadly speaking, though, we can break these down into those that are designed to be worn, versus those that are designed to be attached to a weapon.

Head Mounts

While these devices can be used effectively while hand-held, they work best when mounted in front of the eyes.

GET A HELMET AND MOUNT!

For decades night vision devices have come in a kit with a head mount, typically referred to as a “skull crusher.”  As you can tell from the name, these are uncomfortable to use for a long period or time.  I won’t say “throw it away” since that might affect resale value; instead I will strongly encourage you to buy something like an Ops Core FAST helmet for $200 or so, and use a flip-up mount for your night vision device.  These are more comfortable than a football helmet, and are way more comfortable than the old Kevlar helmets we were issued in the 1990′s.  If you’re going to use night vision, buy a helmet.  You may feel stupid and look dorky (my wife’s term), but it’s the only real option for extended use in reasonable comfort.  Comfort is a relative term when talking about hanging a couple of pounds off your head for a few hours, but a good helmet and mount will at least minimize discomfort.

Just make sure that the mount you buy fits your night vision device.  There are lots of choices here.

Housing Option 1: Monocular

The entry-level unit is the monocular.  These have one objective lens, one tube, and one ocular lens.  The most common design is the PVS-14, and lots of options including weapon mounts are available.  I don’t know that the model you choose really matters all that much, but if you’re going to wear it around then make sure the magnification is 1x, rather than something close to that.  If not you’ll get headaches.

In use a monocular is mounted to your helmet and turned on.  One eye sees the green amplified image, and the other eye is allowed to adjust to the dark.  The end result is that your brain blends both images automatically, so you might have more of a sense of your surroundings than if both eyes were limited to the monocular’s field of view.  To many this usage method is a real advantage over the other housings.

On the other hand, wearing a monocular like this feels kind of weird and unnatural.

Housing Option 2: Bi-Ocular

Here we have one objective lens, one tube, and two ocular lenses which each receive the same image.  It’s like a monocular that has two eyepieces.  These have always seemed more natural to me, probably because these were what we were issued in the early 1990′s, so I learned on these things.

In my experience these are easier to use and more comfortable than monoculars.  You get to see the same image with both eyes which seems more natural, even though you have no depth perception.  Here’s where it gets interesting: there was a study produced by the Army Research Laboratory nearly two decades ago that looked at soldier performance with these various types of night vision housings.  It’s called A Comparison of Monocular, Biocular, and Binocular Night Vision Goggles for Traversing Off-road Terrain on Foot.

Basically, a bunch of soldiers were taken to a Boy Scout camp at night, and told to do land navigation tasks while wearing different night vision devices.  Graders watched and recorded how well they did, and the soldiers were asked to fill out a survey later.  The grading was on how well they could navigate the terrain without falling, mis-stepping, and so forth.

Here’s the soldiers’ perception of the night vision devices:

Here’s the actual data from the test:

 

Total time for the land navigation course was indistinguishable between monocular and bi-ocular wearers.  Total number of errors was about the same, with a slight (though probably not statistically significant) edge for the monocular.  But the subjective experience as indicated by survey results favored the bi-ocular design.

So in use they seem comparable, but many users prefer the experience of using PVS-7′s versus a monocular like the PVS-14.

Housing Option 3: Binoculars/Goggles

Note up front that when I say “binoculars” here I’m referring to what most normal people would call “goggles.”  Two tube assemblies are used, each with their own objective lens and eyepiece, so each eye gets an independent image with no magnification.

For measurement of the advantages of this design look at the data from the study quoted above – it was the clear winner in both objective and subjective measures.

Goggle designs that have two tubes cost about twice as much as the other options, and possibly a little bit more.  In exchange, they offer:

• Depth perception in all light levels.
• The best user experience.
• The best image quality.  Historically this is because the dual-tube designs were designated for pilots, so the best tubes went into these units.  Nowadays we still see the best tubes going into goggles, because the pickiest users (self-selected as those willing to spend stupid amounts of money for the best night vision experience) are buying goggles, and the lower-grade tubes are put into the lower-end units that less demanding users use.

 

Which Night Vision Device to Choose for Head Mounting?

Well, how much money do you have?  Among users who have access to all designs, I can generalize and say that:

1. The vast majority of users prefer binoculars/goggles over either monocular or bi-ocular designs.  These are clearly superior in every way other than weight.  They’re priced out of most people’s budget, however.
2. Some folks have a strong preference for the monocular over the binoculars because of the field of view/peripheral vision issue.  These are a minority, but a vocal minority.

At the end of the day you’re going to have to weigh the advantages and disadvantages of each design and make a choice.   PVS-7 style bi-oculars are comfortable and usable, but you lose the ability to mount it to a weapon (not recommended anyway), mount it to your camera conveniently, hang it off the back of your spotting scope, etc.  It also takes up more space.   Another ShootingReviews author told me how he nearly killed himself on a night march with PVS-7′s because he walked into a 9′ pit with his 100lb rucksack on.

The PVS-14 style monocular is small, is the cheapest option, and has the widest range of accessories available.  In use, though, you’re looking at the world with one eye amplified and one not.  It works fine, but you may find it’s not as comfortable as the other options.

Weapon Mounting

There are three ways to go here: you can mount a night vision monocular behind your optic, in front of your optic, or use a dedicated sight.

PVS-14 mounted behind NV compatible optics

I had a detailed section here, but I’ll simply replace it by saying “don’t do this — buy a laser for your rifle instead.”

Here’s a good thread on this topic over on THR, and some Internet searches should show that this is the dominant opinion among folks that actually shoot at night.

It looks cool, but you don’t want to actually have to use your rifle that way.  Here’s another thread that covers some of the mishaps that can occur with this sort of setup.

Mounting a Monocular in front of your optics

I’ll start with this warning: you’ll pay as much for one of these units as you will for a good set of NV goggles.  The two units you should probably be looking at right now are marketed as the CNVD and CNVD-LR, as they seem to be among the best choices here in the start of 2013.  If you’re going to search for these, the term you want to search on is “clip on night sight.”  ModArmory offers a number of them on this page.

I have no direct experience with these, but Tom Lancaster had a great review of these options on this thread on THR.  In general, these sorts of devices can perform well at magnifications up to 12x, and point of impact shift should be less than 1 minute of angle, but you should definitely test this for yourself.  If you want to shoot at night beyond a couple of hundred yards, then this is the best solution going right now.  Note that you’ll probably be mounting something like a DBAL-2 laser as well, if only because its illuminator can be essential for making the shot if the light level is too low.

Dedicated night vision rifle scopes.

There are a large variety of these available, generally in 3, 4, or 6 power scopes.  The technology behind these is comparable to that in a monocular (using the same tubes), except they offer a reticle, elevation and windage adjustments, and magnification.

I’ve never investigated these much because, well, they’re too specialized.  They’re only usable at night.  You can take a clip-on night sight as listed above and engage minute-of-angle targets out to 1,000 yards during day time with a standard optic, and at night via the use of the clip-on sight.  I suppose it’s possible to do something comparable with a really good quick-release mount and good indexing on your rifle, but I doubt remounting a “return to zero” scope will be precise enough, at least not enough for those of us who occasionally shoot 8″ targets at 800 yards.

If you dedicate a particular rifle for hog hunting then this might make a lot of sense for you, but it’s not for most of us.

Tube Choices

Here’s the part I put off as long as I could, because it’s the most complicated part.  Choosing a tube.

This is going to be really, really complicated.  There are a number of issues you’ll need to overcome:

• Gen3 night vision has been around for nearly thirty years now.  The first PVS-7A goggles were issued in 1985, and used Gen3 tubes.  Needless to say, performance improvements have been ongoing, so there are lots of generations of tubes that can legitimately be called Gen3, each of which performs differently.
• Every tube has its own personality.  I’m looking at the data sheets for two “matched” tubes, and each are rated on 17 different quantifiable measurements.  There’s quite a range on these too — minimum signal to noise ratio on current tubes is 24.1, but I know of some tubes that score over 33.
• Tubes are often identified by “contract,” rather than feature set or capabilities.  For instance, I’ve got an “OMNI-III” tube that was manufactured while the “OMNI-IV” contract was running and was probably manufactured to OMNI-IV specifications.  Why?  I honestly don’t know.
• Manufacturer.  Litton (now owned by L3) and ITT (now owned by Excelis) both manufacture tubes.  They compete, and manufacture tubes that are mostly comparable.
• FUD.  You need to do your homework rather than taking everything at face value.

So, on to the issues you’ll be considering when shopping for tubes.

ITT or Litton?

The short answer is that it doesn’t matter.  The individual variation between tubes that come off a particular assembly line matters more than the differences between the assembly lines themselves.

The longer answer is that in general, the ITT Pinnacle® Thin-film tubes produce a brighter and cleaner image than tubes that use a normal film.  However, the L3 Infinity® Unfilmed tubes are probably better in low light than the ITT Pinnacle®.  All the reports I’ve seen indicate that the unfilmed L3 tubes can produce images in light levels low enough that the ITT Pinnacle tube needs supplemental illumination.

The general rule stands though: normal variations between individual tubes matter more than manufacturer or what OMNI contract they were created under.

Do I want to pay extra for “hand selected” tubes?

Probably.  Paying 5% more to get the best image quality a particular vendor can provide is probably worth it.

What’s up with spec sheets?

Commercial tubes come from the factory with a test data sheet that tells you exactly how your tube rated on various tests.  It’s the only objective indication of the performance level of the tubes you buy.  Whether this matters or not is up to you, but it’s probably most important when it comes to resale.  If I’m selling you a unit that’s guaranteed to have a minimum resolution of 64 lp/mm and S/N ratio of 24 then that’s worth whatever it’s worth.  If I can prove that this particular tube actually has 72 lp/mm resolution and a S/N ratio of 30, then that’s worth more because it’s clearly a better performing tube.

New tubes sold commercially come with data sheets.  Most used units don’t.  Many night vision tubes sold by retailers don’t.  Sometimes these are military contract overruns (where they’re all guaranteed to meet the minimum specification but actual performance isn’t quantified, and it’s possible the manufacturer routed the best tubes through commercial channels and filled the government contract with the more average stuff.)   It could be because the tubes are Gen3 as promised, but they’re second-hand from trade-ins.  It may be that the retailer buys components that didn’t pass initial quality inspection from L3, and the retailer rebuilt them and is selling them as “New L3 filmless tubes.”  Maybe someone got their hands on a batch of unused tubes that were manufactured in 2002 and are just now being put together into PVS-14s and sold as “New ITT Gen3 tubes.”

If you don’t buy new, with a spec sheet, you don’t know the performance of your new tube.  If you don’t pay close attention and buy from a reputable vendor, then you might not know what tube is really in your housing.  Is it worth the extra money?  Only you can decide.

A brief word on vendors

There are lots of companies that sell night vision equipment.  There are lots of individuals who sell night vision equipment.  As I mentioned above — all you need to do is buy a tube and a housing, put them together, and (hopefully) purge the thing with nitrogen, and you’ve built a night vision device.

The problem you run into is complexity, and the different wording that most vendors use.  ”Brand new ITT Gen3 Tube” could mean one made in 1995 and still in the original wrapper.  ”Genuine Autogated ITT Thin Film Tube” could mean it came out of a used trade-in unit.  It could also be that the vendor you’re buying from (or their upstream supplier) wasn’t exactly ethical in the way they acquired or described the components put into their devices.  It’s really hard to tell unless you’ve been around the block a few times, in which case you’ve probably been ripped off or disappointed, or know someone else who was.

There’s peace of mind to be had from buying from an ethical vendor.  It might cost more to do so, but it’s something to consider.

Vendors I would buy from without concern include:

• Frankie at ASM Night Vision.  His web site doesn’t carry his inventory, and his inventory is variable, but he’s honest and will get you what you want if he can.  His prices are very reasonable as well.  He carries everything from the latest and greatest hand selected L3 unfilmed tubes, to blemished tubes with great specifications at a hefty discount, all the way to used units.  Give him a call and you might get exactly what you want at a great price.  Or maybe he’ll tell you he can’t help you.  (When I say “exactly what you want,” what I mean is he’ll work to understand your needs and find the right gear that fits your needs and your budget, and his solution set encompass more than just selling you new gear.)
• Camille at ModArmory.  Odds are you’ll see what you want on the web page and can order it from there, but Camille is knowledgeable and patient if you’ve got questions.  If you ask odd questions she’ll find the answer, even if she has to query an optometrist to get a definitive answer.  (You can guess how I know this.)
• The folks at TNVC.  They are pleasant and helpful on the phone, they carry a lot of inventory, and there are some units you can only buy from them.  Pricing is pretty close to retail, and one the time I called in and requested advice I ended up getting a great product, but in hindsight it was also the most expensive and full-featured of the options I was looking at.  TNVC has great salesmanship.

Something else to keep in mind: If you buy something from ASM Night Vision they’ll probably take it back if you don’t like it.  Both ModArmory and TNVC have restocking fees of 15-20%.  Make sure you know what you’re ordering when you place your order, because an $800 restocking fee for returning a $4,000 item sucks.

Other Vendors

Caveat emptor.  The problem is that there are some very questionable vendors out there.  At least one is apparently buying rejected tubes from L3, repotting them, and then selling them as new tubes without any indication that their performance is questionable at best and probably poor   A big marketing budget doesn’t necessarily mean you want to buy the product being marketed.  Buying from a reseller or from Amazon runs the same risks — I”d prefer to buy from one of the vendors I mentioned, even if it means paying a little more (though it probably doesn’t.)

 

Buying used

Used is a great way to get a hefty discount off of the new cost of a unit, and as explained above the performance of 10-15 year old gear is often still quite respectable.  You won’t know how many hours it’s been used, but with an average life span of 5,000 – 20,000 hours depending on who you talk to it’s probably got some life left.  It could have taken damage from a fall or something so test it out.

It could also be a stolen military unit, which you really don’t want to buy.  Or it could be pieced together from various used parts, which can be fine if the price is right.  Just be aware you’re taking a gamble.

Performance Differences Over Time

Night vision devices are designed to be looked through, and your eye can pull way more detail from a tube than any camera can.  The range of brightness and tones out of the tube is just too extreme, so you lose details in the highlights and shadows, along with the subtle feel for noise that goes away with long exposures or the compression video is subjected to on the Youtube.

Regardless, here’s a comparison between two tubes: one is a blemished (see the black spots) L3 unfilmed Infinity tube in a monocular mount, and the other is an older OMNI-III contract tube mounted in a set of PVS-7s.  The obvious difference is the color: a different phosphor is used in each that accounts for this.

Now, look at the performance between both of these, and use that to help guide your decision on how much more the performance of a new tube is worth.

Indoors, plenty of light

Issues like signal-to-noise ratio make a big difference as the light levels decrease, but if there’s enough light, or if you use an IR illuminator, most of these differences go away:

First is the tube manufactured in 1997.  The red light is my fault: the PVS-7 has a red LED in one eyepiece that comes on if the battery is low, and another in the second eyepiece that comes on with the IR illumination is turned on.  I was using the IR illiminator, and I chose the wrong eyepiece to film from:

Now, compare that to the unfilmed tube.  Ignore the black spots — those being there meant I got this tube for a steal.  You’ll also see kind of a dark donut – this is caused by the on-board illumination as the IR LED isn’t as even as it could be (blame the mini minocular mount, not the tube):

The difference is surprisingly slim.  Looking through the tubes the watch was easy to read and the text was very legible, but moreso with the newer tube as one would expect.  Both were fully functional with the on-board light, however.

Outdoors, no moon

This is a tougher test for the tubes.

Again, it’s hard to see the nuances in detail, but here’s the best I could do:

From another forum

Here is a thread where various tubes are tested and compared.  You can easily see the different levels of performance different tubes offer in various lighting conditions.

What’s it worth?

Both devices filmed above are perfectly useful in the vast majority of lighting conditions.  Even in low light (no moon, cloudy) I can still creep up on deer behind my house with the older tube.  The newer tube, of course, is nicer and brighter, and has more detail.  This is probably most noticeable at range: I’ve got some black steel silhouettes in front of a berm covered in black plastic sheeting about 110 yards from where I shot that video.  It’s hard to make out in dim conditions like in the video, but I can make it out from farther away with the newer tube.

So what’s the difference in performance worth?  That’s a subjective call – gather what information you can and decide what works best for you.  Don’t just assume that you need to buy the latest and greatest (with the highest mark-up) however.  It all works reasonably well.

Tube Specifications and Features

If you’ve done any shopping for night vision you know that there are all sorts of tubes available.  Below are some of the features that I think are most important.

Autogating

Here’s a solid explanation from Photonis.

Basically, autogating is a feature that cycles the power to the tube on and off quickly.  You won’t notice the power cycling directly, though you may have noticed that my camera caught some of that in the movie above.

The goals of autogating include:

• Reduce halo from bright light sources
• Protect the tube from bright light sources in the frame.  Tubes can burn in, and this makes them more resilient.
• Allow the tube to be used more effectively in the twilight hours between dark and light times of day.
• Allow better performance (and reduce damage) from use in bright light.  So if you’re assaulting a house and someone turns on the light, the autogated tubes are supposed to deliver 90% or so of their normal resolution, where non-gated tubes would only deliver ~ 20%.  Plus, you know, damage to your expensive tube which you can worry about after the firefight.  The autogated tubes also won’t be unusable for a couple of seconds while the auto brightness control kicks in, either.

Autogated tubes have a slight whine to them.  This can vary — in my high resolution tube with the blemishes it’s quite noticable; in other units you won’t notice it at all.

This is a promotional Youtube video that shows a couple of examples of autogating:

Note that this is different than Auto Brightness Control which has been around forever and which all tubes pretty much support.  Maybe. I’ve never used tubes/housings with manual gain, so I can’t comment there.

Thin film, thick film, filmless/unfilmed

I covered this up above.  The best performance will come from the highest-spec tubes, which will be either thin-film (ITT) or unfilmed (L3).  At least this is the case in early 2013.

Resolution.

This is a function of the tube and the optics in the housing.  Higher resolution translates into a sharper image, and higher numbers are better.

As a rule of thumb you can assume 72 lp/mm (that’s line pairs per millimeter) is comparable to normal 20/20 vision.  Whether you need this level of resolution (and are willing to pay for it) is another question entirely.  The difference between 57 lp/mm and 72 lp/mm (see the videos above) is noticeable, but it’s probably not as great as the numbers themselves would lead you to believe.

Signal to Noise Ratio

Again, Photonis has a great page on this.  I can explain in detail using high ISO performance in cameras as a metaphor, but basically less noise is better, and a higher signal-to-noise ratio means less noise.

This doesn’t matter at all if you’re going to be working with plenty of illumination (see the short videos above), but as light levels get lower this matters more.  My understanding is that the DoD has stopped worrying about resolution above 64 lp/mm, and instead they see signal-to-noise ratio is the determinant for quality night vision.

I can’t really disagree.

How Specifications are Advertised

Here’s a screenshot from a dealer’s web site from one of their many PVS-14 pages:

If you buy this device, you know it’s got at least a 24.1 SNR and 64 lp/mm resolution, because ITT wouldn’t have allowed the tube to pass quality control otherwise because those are the minimum specifications for the OMNI-VII contract.  If you’re not buying a new commercial tube with a spec sheet, then this is all you’ll know about the tube.  And every dealer will describe available tubes slightly differently, and you’ll also find every dealer has multiple grades/types of tubes (again with unique descriptions or names), with hand-select tubes as an option.

This isn’t saying you will get a 72 lp/mm tube.  It’s saying you’ll get at least 64 lp/mm, but the performance of each tube will vary.

Blemishes

Here’s one where I seem to feel differently than most people.  I like tubes that perform well, and I’m OK with a few obvious blemishes on a tube if I can get it for a cheaper price.

Here’s an example:

See that blotch in the top-center of the frame?  And the smaller black speck towards the right center?  And a few more scattered over the frame if you zoom in?  Yeah, those things are blemishes in “Zone 1″ of the tube, and they will keep the tube from being sold at full price.  Sometimes you can find these blemished tubes with superb resolution, SnR, etc for a huge discount because there are some specks visible.  This tube is one of those.

I never even notice the specks while I’m using the tube, and I’m happy to get an “ugly” tube with high performance for many hundreds of dollars less than a clean tube with average performance.  Other people prefer a pristine, perfectly clear tube and will give up on performance (and pay more) to get it.

Which leaves these blemished tubes available and inexpensive for folks who feel like I do.

And That’s It

That’s a basic overview of what’s out there.  From here you’ll need to do your own research.  There are plenty of sources on the ‘net, but you need to be aware that most of these are put out by folks with a vested interest in the message you take from the material.  For instance: read the PDF file at this link.  Lots of solid information from someone much more qualified to give a dissertation on image intensifier tube specifications than I am (I’m just a user).  Just be aware that the company making the filmless tubes being compared with Gen3 in that report needs to find a way to distinguish themselves, and they’re using MTF to do it.  Keep that caveat in mind, along with the knowledge that MTF isn’t measured for most night vision devices because the US Government never made MTF part of the selection criteria, and you should be good.

All of the information you find out there will be the same — expect some bias, either because companies have a vested interest in portraying their products well, or because someone really stretched his budget to buy a particular piece of gear that he has a strong emotional attachment to.  Fanboys exist everywhere, and the more they spend the more biased they can become.  And quality night vision isn’t cheap.

This is a small market for expensive products, and there’s enough complexity out there that unethical vendors can route you into higher margin equipment while keeping you slightly confused about what you’re actually buying.  And let’s be honest: most people aren’t going to crack open their $4,000 night vision device that’s been nitrogen purged at the factory to look at the image intensification tube.  There’s a lot of trust between vendor and purchaser, and you need to do your research up front.

I hope this article helps you in that process.