Now, my only experience with NV is a Gen3A NYX-14 handheld/helmet mount unit. Since the NV coverts the optical image to electrons an then converts the intensified electrons back to optical light using a phosphor screen, there is some “resolution” associated with a NV device.

Say I want to put NV on a rifle... like a suppressed 300BLK or 308win or something and shoot further than just a helmet mounted device would allow.

Wouldn’t putting even great Nightvision in front of a nice scope just result in magnifying an image that is still limited by the ITT itself? Kind of like blowing up a low resolution image in photoshop... ?

Wouldn’t it make more sense to put a PVS-style NV unit BEHIND a good riflescope (like you’d put NV behind a red dot) rather than the typical clip on NV in front of the scope?

Can someone explain clip on NV to me?

Most clip on have a huge objective lens to bring in light. More light = better, clearer image.

Every lens (or prism) you make the light transmit through, you lose some of it. So if you put it through a big rifle scope with a bunch of lenses and prisms, you lose a lot of light before it reaches your PVS14.

Try both, then get back to us.  In all seriousness though, clip-ons so thoroughly stomp the shit out of a PVS-14 behind the day scope that the capabilities of each combination aren't even comparable.  I've used NVDs behind day optics from Omni 2 through my current L3 FLAG WP supertube, clip-ons still win BIGLY.

An astonishing amount of light (especially the wavelengths that we want to be incident on the NVD's photocathode) are lost while passing through a day optic's lens system.  Illuminators can help, sometimes substantially, but that same illuminator would be even more beneficial with a clip-on since you don't have a day optic killing off a good portion of its reflected energy.  Then there is the ergonomics of the whole mess, stick a PVS-14 between your eye and the day optic comfortably and without interfering with your charging handle (assuming an AR platform).  Then there is getting the focus right...  Yep, it can be done and I did it occasionally for 10+ years.  Hits out to 200 yd even (in retrospect, not far at all).  W/o a powerful IR illuminator, I couldn't shoot far.  I came up with a ton of different ways to make it work just to avoid buying a clip-on.  In 2017 I decided I was going to get it to the point that I could reasonably and quickly get hits out to 500 yd or buy a clip-on.  Then, I bought a clip-on NV.  Then, I bought more clip-ons.

Clip-ons are not handicapped by light loss through the day scope in the same fashion that a downstream NVD is.  The good ones have an appropriately large, high quality, fast objective lens up front to pull in all the ambient optical information reasonably available.  Couple that with a good tube, collimation or some sort of user adjustable boresighting, harden it against the elements/recoil and WHAM...  mil-spec clip-on.  The size and quality of that objective lens on a clip-on is extremely important if you intend to shoot long distance, though.  A month or so ago I was out distance shooting at night, I could easily see the ~2 MOA steel targets all the way from 100 to 1000 yd.  I only had dope for that gun out to 600 yd, and that distance was EASY.  No illuminator, none needed.  I had my 14 rigged up to my spotting scope that night and couldn't see shit without illumination.  Even with it, nowhere near the detail (14 was L3 FLAG supertube, no slouch).  All this and it was easy, comfortable shooting.  No head/neck cranking, stock extenders, relocating day optic, etc.  I will never go back.  My 14 now stays where it belongs, on my head.

Bottom line, if you like shooting distance and would like to do so at night (and you have somewhere to do it) then buy a NV clip-on.

@fordkicksass

Thanks for the detailed insight.

Do dedicated ITT-based NV rifle scopes also share this inherent advantage over putting something like a PVS-14 behind a daylight optic? It seems like, if so, it might make more sense to buy a daylight optic, and then a dedicated NV Riflescope rather than deal with the added bulk, length, weight and alignment issues of putting a clip on in front of your existing daylight scope. Also, given your description of the inherent advantage of a Clip-on (in front of the scope) vs a quality Gen-3 unit (behind the scope), that you could save some money and still get very good performance from a Gen 2 or 2+ ITT in the clip on role?

My D740 Thin Filmed kicks my two thin filmed monoculars ass.

Of course, it has a 100mm lens to gather light. I think a PVS14 is something like 30mm.

The negative is that while removing and replacing the optics is possible, you’re not likely to have as good an RTZ as a clip on (and you’re worrying about that for TWO optics instead of one), nor will you likely have as high a magnification with the dedicated night scope.

Yep, a quality dedicated night vision weapon sight also produces an image far superior to a NOD behind a day scope.  They are great, my favorite of the ones I have owned is hands down the NVEC Raptor 6x.  Oddly enough, the cascade gen 1 Zeiss Z51 Orion is my second favorite.  Crazy good image for the price .  Yes, there is usually a weight savings from going dedicated instead of day optic plus clip-on (PVS-2 anyone?).  There are a few reasons I have moved on from dedicated scopes, but others' experience will invariably differ.

1.  Reticle.  Even the mil-dot reticle of the Raptor didn't do it for me.  It is perfectly usable, but I have become far too spoiled with modern riflescope reticles.  If I am shooting longer distance than I want to use my 14 and IR laser for, then I want a reticle that allows for accurate holdovers including wind.  As such, I want to be able to still use the same reticle at night that I use during the day.  Clip-ons make that a reality.  I can go from zero to the limit of the reticle (currently 800 yd w/ my 5.56) during the daytime or nighttime without touching anything but the clip-on's focus.  I can dial to go further, but that is slower and also the SWR Radius will no longer be aligned with the center of my reticle.

2.  RETICLE!!  (see above )

3.  Variable magnification.  Do you like variable power during the daytime?  Of course you do, so why not have it at nighttime too?  I can have a wide FOV @ ~3x and then go up to 8x or 10x for the shot.  8x seems to be about perfect for me so far.

4.  Can move between different rifles without changing anything.

5.  No removing the day optic.  A good QD scope mount like a LaRue makes this less of an issue, but I still prefer to keep my primary optic right where it belongs.

Many, many people prefer dedicated scopes.  I am not one of them.

One thing to consider when getting a clip on is loss of resolution.

Unless your day-optic matches the magnification of the clip-on, you'll lose on resolution.

Say you use a 8x scope on a 3x clip-on, you'll lose over half the resolution, because you actually zoom into the phosphor screen of the tube and thus cut out a lot of the remaining tube image.

I would skip anything Gen 2. Dedicated scopes are always better than adding a PVS14 behind.

One of the members here use to post that he would switch from his day optic to a dedicated NV scope (as I recall a D740) easily in the field with no issues with regards to RTZ. As I recall both scopes were equipped with LaRue QD mounts. So will switching from a day optic to dedicated NV save weight and bulk, absolutely.  I did this myself, but it got old quick.

I have used NV behind days scopes for years actually over twenty four years with 22's. Recently I tried a PVS-14 with 3X lens behind an Aimpoint T-1 and it was total garbage. Without the 3X lens it is fine, but you have no magnification so it is pointless to me. I then went to a Eotech EXPS3-0 in front of the 14 with 3x lens. While the image is great I have found a problem with the Eotechs center dot, it is not a dot, but a revered comma. I have yet to decide if I am going to argue with Eotech over this. One thing I have always wanted to try was a PVS14 behind a Scout Scope.

Something you might consider is what I did years ago. In the past I had the 2-10x and 6-16x McMillan Day/Night scopes. Similar to placing a PVS-14 behind a day scope but in a more sophisticated and solid way as it is purpose built. As I have said in the past the McMillans were a love hate thing. While I loved the concept and the speed at which you could go from day to night there were a couple of short falls. The real issue for me was both models had thin reticles which I found to be a pita at night and even during the day if looking into the shadows or using at twilight. Not that this one was a real downer but unless there was some moon light I generally found the need to introduce some additional IR. The reason I never really found this to be a downer was I liked seeing the eye shine from the predators as it gave me an aiming point. I like to head shoot whenever possible. Now the 6-16 model had a huge 80mm objective lens and the thing was so heavy as a day scope it was a pain in the ass to lug around. As a laymen when it comes to determining the quality of a day scopes glass I honestly cannot say if the glass in the McMillans was good day glass or not, but I always thought if the 2-10 had the best glass and a thicker reticle I would never even look at any other Day/Night set up. Modern version is the Aurora. One of the up sides is you can buy additional Aurora day scopes and just move the Night Vision Module around.

After the McMillans I made the leap to a KAC PVS-26, and while the image is great, the 740 was still better at shorter distances and without the bulk and complexity. As long as you get the heights of your day optic mounts within the correct margin for your Clip-ON using them is them is pretty easy, they just take a little more time to adjust for changing distances. Again, the down side of the KAC is its weight/bulk, and I personally have found that the KAC QD to be a little bit of a pain at times to mount in the dark. As TNVC and other informed members have said the better the day glass the better the image will be, especially the further down range you go.

My dream would be a miniature variable powered PVS10 and if not variable, fixed at 6x or a light weight clip-on good up to 8x with a flip to the side mount like the Wilcox UTM mount. For the life of me I cannot understand why someone cannot invent a PVS-14 that can be mounted in front of a day optic without the need for all the additional add on lenses.

Tried a scout scope and long eye relief Burris around 2008, same abysmal results even with illuminator.  Abysmal compared to a clip-on, that is.

It's worth noting that losses are generally similar whichever way around you put it. The OP's concerns about clipons is not only insightful, it's justified. They really need to be optimized for application and are not as universal as some might believe.

With respect to the optical losses, don't forget that your average PVS-14 has around 90% optical losses in-system and this provides, as a rule of thumb,  that if you start with 70,000 tube gain, you're going to end up with 7,000 system gain once you house the tube. Clipons are usually a lot slower than PVS-14's and I've never heard of a clipon that has lower losses.

Then there's issues with used photocathode area reducing resolution ( and light ) and also FOV mismatch again costing light. Finally there's the induced exit pupil to consider at the eye, which is greatly affected by the scope.

In a rear-mounted clip on, these problems are somewhat eliminated by the design, and the optical coatings don't necessarily remove a lot of light where Gen3 is concerned as it passes through the scope. Most dayscopes don't consider IR at all, but by the same token, they don't do anything to stop it either. Downsides are severely screwing with shooting position, and perhaps the loss of exit pupil works the other way against the user also. Aperture of the optics also affects the outcome and again, the full FOV may not be available = more losses.

This perhaps is why clipons are chosen over rear-mounted look-through systems... Convenience.

If light losses were equivalent between the two systems, shouldn't the resultant image of each be of comparable brightness?  In practice, the image produced by a quality I^2 clip-on/day optic combination seems to always be significantly brighter than a day optic/PVS-14 combination.  Day optic coatings are not optimized to transmit near-infrared light wavelengths, there would be no point in doing so.  I don't have a number, but the loss of relevant near-infrared wavelength light must be positively astronomical inside even good day optics.  One needs only to look at an IR illuminator through their 14, then that same illuminator through the day optic/14 combination to see this in practice.  The difference is night and day, pun intended.  A clip-on, like a 14, is designed to convert near-infrared wavelengths into visible wavelengths (I realize this is common knowledge, just stating it as part of my rationale).  Green and white colors (the most common colors of phosphor screens) are both obviously in the visible spectrum and, therefore, should be transmitted through a day optic with better efficiency.  I am not an optical engineer, but that seems logical and the experience of myself and others seems to support it.  The OP's question is absolutely valid, I had the same question and so have many others who have looked at the situation analytically.  Looking back, however, I wish I would've bought a clip-on the SECOND I could've afforded one instead of trying fifty different ways to make my PVS-14/day optic combo do what I wanted it to  It would be extremely interesting if someone with technical manufacturing insight into this question would stop by, we could all learn something.

You're not incorrect in that the losses will be higher due to most coatings optimizing around 600nm ( a guess ) but they are broad spectrum, and at around 800-850nm, they may not "anti-reflect" as much but they probably don't block the light either. It is probably very dependent on the particular scope and coatings also. By around 1100nm, it would be a different story I imagine as the coatings should start to reject the wavelengths, but this isn't relevant to us at all. Noise would be higher due to the mechanics of the image intensifier, but brightness may not vary as much, assuming the tube ABC is operating. ABC will likely drop out first if the monocular is behind the dayscope, due to the loss of light to the photocathode, but the amplification effect will otherwise try it's best to push more light to the eye since that stage is now closer to the eye.

This actually means that you should generally get a brighter image to the eye, but noisier. ( ie, light output from a tube should be constant, so it's light from an ocular lens, or light from an ocular lens, through a dayscope - obviously the dayscope will lose more light ). This will change of course as the tube's input signal drops into the linear amplification range. Ultimately, if you graphed each system for just brightness, I'd expect the lines to cross twice.

Putting the monocular/clip-on in front of the dayscope will reduce the light in some cases, but your eye does a pretty good job of compensating.

I won't question your choice - I'd do the same... If I could just go straight clip-on ( although I do have dedicated, which I prefer ) over rear-mounted, I'd do that. But the reason people go rear-mounted is just budget and resources. Also, it's still an effective way to shoot with high accuracy though does often require an illuminator to make up for the light lost initially to the photocathode on darker nights. It's a bit like why sometimes, Gen1 is still better than no night vision at all.

David.

There is an Armasight MR Gen2+ on TexasGunTrader (seller is out of Houston), for $1200, btw.

Not affiliated in any way.
https://texasguntrader.com/category/570/Guns-for-Sale-Rifles/listings/1310016/ARMASIGHT-CO-MR-GEN-2-CLIP-ON-NIGHT-VISION.html

A brief video illustrating a decent clip-on and what it looks like to the naked eye without throwing it in front of your scope. The optics within it reduce the size of the intensified image to be optimally viewed through some magnification. 4-10 power are all pretty decent with this one.

Nice vid!