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Discussion Starter · #1 ·
So, someone in some thread I can't find now asked about NV pictures of the PS90 USG sight. I saw another thread that had some but the pictures were unfortunately gone, so here's my attempt.


- PS90 USG

- Night Optics D-121 Monocular
- - - Generation: II
- - - Tube: 18mm, US-made, milspec
- - - Resolution: 32 LP/mm
- - - S:N Ratio: 6.3
- - - Photo Sensitivity: 493 ma/lumen (@2856K)
- - - Luminance Gain: 12345 FL/fcd (@???fc)

- Sony DSC-W90 digital camera (8.1 MP, F2.8, optical IS)

- Sony DSC-H50 digital camera (9.1 MP, F2.7, optical IS, 15x zoom, NightShot, manual mode, remote)

While the DSC-H50 is a better camera, the W90 "mates" to the scope better so I tend to use those images as they usually came out somewhat more clearly (I don't have the "real" camera adapter(s)).

Photo Shoot #1: Rural Mountain Road
- 11pm, winter, overcast, no starlight, no moon.
- heavy tree cover limits available light further
- pretty much a worse-case scenario for NV

So, as it turns out, trying to hold a digital camera, rifle, and night vision all perfectly aligned on an icy mountain road when your hands are numb is hard. I ended up lying supine with the PS90 held between my legs and the NV scope in one hand, and the digital camera in the other. I used high ISO mode which produces really terrible images because of low light and excessive camera shake. Seriously, I tried for 30 minutes or so to get these right, and these two are the best I got, so apologies...

Aimed at sky; VERY dark and yet the NV scope still dimmed due to the brightness of the sight. Focused at infinity, so as with using the scope with your eye, there essentially appears to be a magically floating crosshair as everything else is out of focus.

Similar set-up to the above image, but focused near (on PS90) instead. As you can see, the tritium vials (trasers) in the sight are blindingly bright to the NV scope.

Then, I headed down the road, trying not to slip on the ice with my PS90 in one hand and using my night vision headmount for navigation. Well, that'll teach me to leave my YakTrax in the car. It was so dark I had to use the IR illuminator to see any real ground detail while walking.

Photo Shoot #2: House
- Brightness about that of a starlit night
- Target objects ~10 feet from camera
- PS90 in sight vise, NV scope resting on magazine looking into sight, camera handheld for the DSC-W90 shots, and remote used for DSC-H50 shots.
- EV adjusted to approximate looking through the NV scope with my eye

So I wasn't happy with the above photos and wanted to get something a little less hideous for you guys, but I was damn cold and wanted a more stable setup.

I'm sure some of you will recognize the objects used in the target shoot.

(DSC-W90) This is the setup without the NV scope being used. Instead, a flashlight set to 10 lumens is used for illumination. You can see both the daytime black and tritium recticles.

(DSC-H50) 30-second manual exposure, F2.7, ISO400. Yes, it really is relatively dark.)

(DSC-H50) No NV scope used; here the camera is set to Sony "NightShot" mode, which sets a very high ISO and removes the IR filter. A IR illuminator is also activated, which I'd approximate is about 5 lumens. Please note the IR illuminator does not fare well at distance beyond a couple of feet, and without it, NightShot mode is less sensitive than your eye. Further, the preview image is darker still because the high framerate negates leaving the shutter open for very long. So, in other words, NightShot is only practical as a ghetto NV scope if you have an external IR illuminator. I tried a shot here while blocking the IR illuminator LED and it was all black.)

(DSC-W90) This is the target without the sight, ambient light only.

(DSC-W90) Above only with the sight now. Notice how the tritium is too bright, forcing the NV scope to gain down and thus lose the target. Everything is a black blob, whereas before you could clearly identify a distinct shape for Mr. Bubbles and the Pip Boy.

(DSC-W90) The above image with a flashlight set to 3 lumens for illumination. This allows the target to be visible even at the lowered gain setting. With my eye in place of the camera in this shot, I could read the words "Vault-Tec" on the lunchbox.

Lessons Learned

- Too Bright - The PS90 USG scope's tritium is too bright for passive "starlight" use, as it forces the NV sight to "gain down". I suspect urban environments and moonlight would provide enough ambient light to maintain some sort of target acquisition after it's gained down.

- Severe Interfacing Problems - Aligning a NV scope, either handheld or headmount, is difficult because the FOV on the sight and recticle is very, very narrow. If you're trying to actually hold the PS90 normally against your shoulder and do a cheek weld, uh, good luck. The maker of the sight does make a NV mount adapter for the PS90 but they nor FN will sell it to civilians. Most NV scopes use M1913/picatinny rail-mount adapters, so it's possible that replacing the sight or getting the tri-rail model may be a solution, but that's rather inefficient.

- Odd Color Choice - Red is very dim to the human eye relatively, though it does preserve "natural" night vision and not mess up the dark adaptation of your eye. However, NV scopes (especially gen 3) are hypersensitive to red and IR wavelengths, and gen 3 in particular due to the photocathode material is almost blind to blue light relatively; I believe in aircraft using NV headmounts, they use blue instrumentation and put a filter on the NV scope(s). imo, they should have used blue trasers for better NV compatibility. Even with the factory mount, the problem of the trasers being too damned bright and forcing the tube to gain down still exists.


I would not recommend the USG sight for use with night vision equipment, even if you could purchase a mount, in starlight conditions or worse. The excessive brightness of the trasers for NV gear forces them to gain down and makes the tube's artificially decreased sensitivity only marginally better than the dark-adjusted human eye. Active IR illumination can still be used but this gives away your position and may be a tactical mistake. (perhaps you could argue the P90 was intended for urban combat, and the urban skyglow alone would provide suitable illumination to offset this.)

On a positive note, the red traser color is ideal for preserving natural human night vision, as red light does not break the rhodopsin used to detect light in the rods (low light sensitive element) of the human eye.

Note: While Gen 3, and Gen 3 OMNI VII equipment certainly do outperform my Gen 2 scope, they too would gain down.

(Update 1/20/09: Another member posted in the general PS90 forum that their PVS-14 and white ring sight had the same "dim" issue. The PVS-14 is a gen 3 device, and a very common one in military/LEO use.)

· Registered
17 Posts
Discussion Starter · #2 ·
Update: I performed more testing in an urban environment; I live in a city of about 50K residents, with almost no streetlights in my area, but relatively significant skyglow nonetheless. (I was out of the skyglow on my rural mountain road images).

I found that the NVD somewhat enhanced my visual range and ability to see into shadows, but it was already gaining down pretty significantly, so the trasers did not make it gain down further.

I contacted the OEM of the sight as they advertise it as being night vision compatible with my findings, and I'll let you know what they say (if anything). I also brought up the NV mount question, or rather, its commercial availability.

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Wow, very nice write up!! +1 karma for you!!

· Registered
17 Posts
Discussion Starter · #6 ·
Thanks for the attempt at least ;)

I also want to add that while my conclusions reflect disappointment on my part with the combination, I still really like the PS90 and even the sight; like I said, red is an ideal color for use with the human eye at night. The use of NV in combination with the PS90 would be rare at best for me anyway, and it is only in a minority of situations that this has an impact (non-urban, no moonlight, situation where IR illuminator use is not optimal).

I've also contacted someone with more NV experience than I (and much better equipment) to see what his view on sight brightness with better NV equipment is.

I've thought about this further, and the sight OEM also mentions the tritium vials can be replaced. I will see if I can find out more information about how they are accessed; if so, I see the possibility of a filter mod for NV use.

The reason I go to these lengths and time commitments with this stuff isn't because I'm disappointed or dislike this stuff, but rather, like it quite a bit. I'm quite pleased with my little Stargate carbine thus far ;)

· Banned
4,055 Posts
ick said:
Iceman, did you give him positive karma or negative by accident? I see he had -1 Karma before I gave him +1
I'm positive I gave him +1 but it was a crazy night...

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17 Posts
Discussion Starter · #13 ·
Is that a fallout toy in one of the sight pictures....sweet!
Haha, yes. Fallout 3 lunchbox and bobblehead, along with a big daddy from Bioshock. I could've tossed in the Mirror's Edge runner's bag in the background but that seemed excessive. I'm a sucker for collector's editions.

Also, on a sidenote, I never received a reply to my email inquiries, but I do see another post in the general forum from a PS90 / PVS-14 owner who confirms what the other said-- the sight blooms too much with a gen 3 device to be useful for NV. Perhaps that's one reason FN is offering the factory red dot models now.
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