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AUNV Night Vision Review:
GT-14 Vs MiNi-14 (AKA MUM )
If you're looking for a top quality NV unit then without a doubt, most will recommend the AN/PVS-14. This review, however, is not about the AN/PVS-14. It's about two other similar scopes - The N-Vision Optics LLC GT-14 and the Insight Multi Use Minimonocular NVG ( MUM2 ) more commonly just called the MUM.
Both of these scopes are non-military versions, though it's relevant to point out that the MUM is built to military specification despite it's lack of a Nato Stock Number ( NSN ) and it's also waterproof to 66 feet while the GT-14 is only water resistant.
Both are made of what looks like a hard-wearing plastic and very good lenses. What really sets the two apart though is the price. The GT-14 is considerably cheaper than the MUM.
It's this price difference that leads many to ask, which is better for my use? Can I save a few dollars or do I need to spend the extra and get the kit that I really need? Will the cheaper scope function in place of the more expensive one? What makes up for the difference in price?
This review examines both scopes from a practical perspective to provide an aid in selecting your scope if choosing from these two models. Of significance, these two models are also export models, so can be purchased outside of the US. In fact, the MUM is widely reputed to be the best scope you can buy for non-US dollars. Because of this and perhaps for sheer convenience, I have selected a set of tests that use the European XR5 tube - the xx2540BP. Both scopes have been assembled with these tubes and both are roughly equal from that perspective.
In this way, this review is every bit as relevant to non-US buyers as it is to US buyers.
Both of these scopes are representative of Optics HQ however I should point out that both scopes may or may not have all of the accessories shown through this review. Treat this as an example of what you can order, not what you should get if you order one - Ask Michael what you're actually getting since some items are optional extras or may not be relevant to your configuration.
Now down to the review.
The GT-14 by N-Vision Optics is a great little scope. Priced with the best budget models, it incorporates a very large eyepiece with excellent objective optics and it's all O-ring sealed. The front lens can be removed by twisting, however the rear eyepiece lens has a retaining nut that holds the eyepiece in. The eyepiece is adjusted by turning and is cut for grip and so is the objective.
The GT-14 also has a neat little secret. The front lens is similar in fitting to the AN/PVS-14 so it will directly take the AN/PVS-14 3x adapter meaning you can either screw the larger lens into the objective or fit it over the top clip-on style. This is a great feature and really gives it an extra benefit.
Battery is a CR-123 format cell with a screw-cap that is easy to remove and fit and is also O-ring sealed. The retaining cord for this however often gets in the way of the LED illuminator that is built in, which is a problem.
The lens-cap has a pinhole for checking operation and although there's no cord attaching it to the body, it has a lug and the battery cover retaining strap has a loop so a small thread between them is sufficient to make sure you don't lose your lens cover at night.
Power is by the bulbous rubber switch on the back. Press it in and it's a clicky. One press and it powers up. One more press and it powers down. A long press when powered up will turn on the IR and another long press will turn it off. It's easy enough to find in the dark and works alright, but I can't shake the feeling that it comes across as cheap. Sure, it works OK, but it's just something that feels like it's going to fail like the M703E ENVIS, though I have never heard of a failed GT switch. Perhaps it reminds me of the primer bulb on the bottom of cheap lawnmower carburettors and an incident in which one split and squirted fuel into my eyes a bit too much. Anyway, that's all subjective. During testing the switch functioned flawlessly, though it's mechanism does have one fault. If the tube doesn't power up immediately, you are likely to keep switching it on and off, never really being sure whether it's on or off. Also, it's more likely to get knocked on while travelling if your kit is a little crushed.
Purging is via a little screw that fits into the attachment rail that is found on either side of the housing. There is also a camera tripod threaded received on either rail, which works exceptionally well when you want to tripod mount your NV for any number of reasons. Not to mention that is how many camera adapters attach to your scope, though a nice feature of the GT-14 is that it comes with a camera adapter, though I have no idea what video cameras it fits ( Michael, can you please enlighten us? ) and the manual shows a few options I didn't have, such as the camera attachment bracket of the Yukon style ( which I have an old one of ) and some different weapons mounts.
You can also weapon mount this scope and it's attachments are similar to the MUM's, in fact, interchangeable. There are again different models that the manual shows, though the standard model from OpticsHQ fits both the MUM and the GT14. Having a dovetail rail on both sides, it can be set up for right or left handed use.
The same dovetail allows a J-arm fitment and this permits connection into a headmount ( supplied ) though it will also permit connection to rhino-mounts or other head-mounted kit which allows it to flip-up though it has no auto-off feature or function. A dual-headmount option will allow two units to be used side-by-side for binocular vision.
Other things I noticed about this scope? It comes with a sacrificial lens, a very comprehensive manual and a small packet of lens-cleaning papers. An eyecup finishes it out and overall it's a very nice looking scope with a solid feel that will appeal to anyone.
The MUM or Insight Multi Use Minimonocular is quite different in appearance. The conical objective lens really sets it apart visually and the monocular has an excellent reputation, once having been used by US Navy SEALS for it's underwater capabilities. To that extent, the first thing I'll mention is that it comes with Dive Windows to allow use underwater and I know these units are very favoured by police for this purpose also.
The scope itself has an objective lens that is held in place by the focus lock nut while the rear eyepiece screws in. The objective doesn't easily attach to a 3x lens adapter, however a special fitting will allow these lenses to be screwed on. This is perhaps the greatest weakness of the MUM compared to the GT-14.
Power is via a protected switch, which must be pushed in to rotate, but it works exceptionally well and feels solid. Rotate one way for on, the other for on with IR. There is no difference between the two, other than direction, so under combat conditions, it's possible you might turn the IR light on - quite a problem. It's IR seems a little brighter than the GT-14's but they are both much of a muchness. It is, however, very easy to turn off, even when fumbling, and shuts off with a satisfyingly audible click.
Unlike the GT-14 and most other scopes, the MUM does not take a camera tripod thread, but a 1/4" 20TPI tap makes quick correction of that issue and you can fit your own which, which shallow, is still useful though it means it's not as suitable for quick surveillance use with a cheap metal camera adapter or tripod. ( You'll notice the silver threads inside mine which show that I've already cut two threads in one side ).
Like the GT-14, the MUM is purged by a screw located in the same plce. The body is small and has a nice shape and the focal rings are well knurled and easy to find and operate in the dark, as is the power switch. The battery is similar to the GT-14 but it goes in from the back, so the retaining strap doesn't get in the way and the LED is covered by a waterproof window. Focus is light and easy to turn and the eyecup slips around easily.
Other than the dive windows, it too comes with a manual and some lens papers and also fits to the same weapons mount as the GT-14 being likewise with a dovetail rail on both sides. It's a touch shorter than the GT-14 as well, making it more compact.
Although the MUM is not a military monocular per-se, it is designed to conform to military specifications and this is clear on working with it. Everything about it seems precise, clean and made with purpose, right down to the extra stitching and heavy-duty webbing on the pouch which holds it all. Overall, an excellent scope.
Comparing the two.
Two determine what is needed, both housings were tubed alike. The XR5 xx2540BP is a Slim ANVIS tube manufactured in Europe. It's roughly on par with Gen III Omni V and represents the best of the tubes that can be obtained outside the US. Tubes supplied as Gen2 with these housings will approach it in terms of quality and it is possibly available as an option to those wanting these scopes tubed as such.
These scopes have a resolution approaching 72 lp/mm. Since pictures are not the primary way in which the scopes can be quickly evaluated, I've only taken one picture and under a mix of low and high light conditions to show typical lens performance outside. Other tests have been more specific and are intended to show the lenses apart. Photographs were all taken with the same settings on a Canon PowerShot A590 camera - An excellent choice if you ever want to take some NV photos and a very cheap camera on Ebay although new ones are no longer in production.
Lighting conditions were a dark room with a very small amount of light coming from the next room though the crack while the door was almost shut. This provided consistent light and since the tubes are the same, the amount if light isn't so important, as the lower light affecting MTF only slightly. The target image inside was the same frame. A 1cm cross-hatched high contrast piece of A4 paper. The grids are at 1cm intervals.
Test 1. Center Resolution of a Flat Image.
This test was determined to be likely to show how much of the image remained out of focus when a flat object is looked at. It's pretty much evaluating the blurring due to the Petzval curvature of the lens.
MUM on tripod.
Yes, thatís a MUM on a tripod. I tapped the dovetail for that reason as mentioned earlier and as you can see, it works well.
In this test, both images blurred towards the edge. This isnít necessarily something wrong, but if youíre in a fixed location and looking at a flat wall, itís relevant. It also shows, to some extent, the depth of field within the center and the quality of the lens.
Although when both are stitched together, the full comparison comes out.
Overall, the MUM has slightly better center focus over the range of the lens. To determine whether this is caused by the lens or just how itís set up, I moved the focus to the side of the lens.
Test 2. Lens edge resolution of a diagonal image.
To further test the lenses and optical parts of the housing, I evaluated the lenses out to the edge.
MUM Vs GT14
What this showed is that the GT14 suffered far more from vignetting that the MUM and had slightly lower edge resolution although the MUM wasnít a huge improvement here.
Of interest, the GT14 was far less bright at the edge too - demonstrating clear vignetting ( more on that later ) and also I noticed something else.
In all my tests do far, the GT-14 doesnít have a well-defined edge. Aside from being larger to my camera, itís always got that blur at the very edge.
So I tipped the camera to the side and took another photo. This really shows up a weakness of the GT-14.
And there you have it - The edge of the tube is clear now but thereís something in the GT14 eyepiece that limits what can be seen of the tube and perhaps reduces itís overall image size by a millimetre or so. Image for image, that drops the image resolution that you effectively see by five percent, though itís probably more accurate to say that it reduces the image field of view by five percent.
Test 3. Vignetting.
The Vignetting brings up the final test. How much of the image gets through the lens. This isnít so much a test for relative aperture as a test for light throughput and is directly related to lost light at the edge of field. In ultra-dark environments, this can make or break a scope because serious vignetting will lead to a limited FOV under ultradark conditions.
So the test is simple. With the pinhole cap in place, which lens gives the biggest image? Bigger is better and perfect is no image loss at the edges.
GT14 without flash ( just the image through the pinhole )
GT14 with flash ( Shows up the unused screen around image )
MUM without flash ( Just the image through the pinhole )
MUM with flash ( Shows up the unused screen around the image )
Well, in the other tests, it was close, but this pretty much clinches it. The MUM has an excellent image with a wide area that is unaffected by vignetting.
On the other hand, the GT14 suffers considerably ( itís canít even see the sides of the sheet of paper ) and thatís before you take into consideration that you canít see the edges of the tube anyway.
Test 4. Image Testing.
The image test is the final piece of the puzzle. With artificial and reflected light, the side by side pictures tell you what you really get for your money.
And a PVS-14 for comparison ( Omni VII )
In this picture, the GT-14ís great weakness, the screen-view limiting eyepiece, is clearly not as sharp as the MUM, but both scopes are otherwise more than capable.
Overall, both are excellent scopes. The MUM has clearly better optics under objective test conditions, but the GT14 is no slouch, providing excellent operation at a budget price.
Overall, if I had a GT-14 I wouldnít bother trading up, but there are a few things to consider. First, if itís for underwater use, then itís clearly the MUM. No question. If itís for surveillance, I would probably lean towards the GT-14. For quality itís the MUM. For add-on convenience, itís the GT-14. For style, itís the MUM. For optics and resolution, itís the MUM. For ruggedness, itís pretty much a draw.
Whether youíre a law enforcement officer, pest controller or even a soldier, both are pretty good scopes. In life-critical situations, Iíd probably go with the MUM but even then, I wouldnít turn my nose up at the GT-14. Both scopes are available overseas and outside the US as export models and both are available inside the US in both Gen2 and Gen3.
While thereís no doubt that the MUM is superior to the GT-14, the close results and the fact that the GT-14 is a lot cheaper than the MUM puts them on about the same footing.
So in advising someone who doesnít have a need for a specific feature only available on one unit, then Iíd suggest getting the MUM if you have the extra cash or need it for enforcement or military purposes, since the optics are significantly better. If youíre a little low on budget, then you can go for the GT-14 knowing youíre still getting a great scope for the price.
Whatever your choice, itís pretty hard to miss with both models.
Reviewed by David Kitson, 21st June 2011.