I'm jumping in here a little late... but it seems like the advantages are being pointed out to you, and you're dismissing them.

We can throw around jargon all we want--but seeing two slightly different images in either eye is going to have an effect on depth perception. It's a slightly silly exercise that doesn't necessarily prove anything on its own--but can you do "Magic Eye" or other stereograms?

Try it with binos, and then try it with a set of PVS-7s... you can resolve the image through NVDs with binos because you're replicating stereoscopic vision, you can't with PVS-7s because you're seeing an identical image in both eyes.

The thing to understand about the PVS-7 is that they were invented literally because the Army thought that Infantrymen weren't worth the cost of two tubes. The old PVS-5s were binocular devices, and no one didn't think that binoculars were better--but the thought was that Infantrymen could "get away" with a single tube and cut the cost of NVDs in half, which had its pros and cons--the big pro being the ability to equip more personnel with night vision, the PVS-14 was in turn designed to offer a better solution to the "one tube conceit" that had been established by the PVS-7.

Something to consider is that aviators have never used single tube systems, they're moving faster, and dealing with more complex spatial relationships, one has to ask oneself, "why is that?"

The question to ask, especially when spending your own money, and not the government's is to look at what folks who don't have to ask "how much" are using and why, rather than the folks who are asking "what can we get away with?" This is not to say we're not all going to be able to afford what those guys are using, but tracing their reasoning back to the source can help you better interrogate your own needs.

So, I've been preaching what makes binos better than bioculars, and many may say "sure, duh, they cost upwards of 5-6 times as much as 7s, but what makes 14s better than 7s" besides the weight/form factor?

So here goes:

In all but the darkest of conditions, the PVS-14 will give you superior depth perception because your unaided eye is still processing some information, though you may not be fully conscious of it.

The manual gain controls which allow you to adjust the brightness of the tube will in fact be a great aid in ensuring that you pick up as much supplementary information as possible without your brain being "overwhelmed" by the sensory information from your NV aided eye.

In conditions so dark that you can't pick up any supplementary information, using a single tube, you're essentially "on par" with a PVS-7 for depth perception.

Nevertheless, some people report the PVS-7s to be comfortable or generally "friendlier" than PVS-14s, what's that all about?

IMHO and IME--it's because the PVS-7s are tricking your brain.

To a certain extent, this goes back to why the Army thought that PVS-7s were a good idea in the first place, coming off of dual tube goggles.

What PVS-7s do is to give both of your eyes an aided NV view through a single, center-mounted tube.

You are not a cyclops, and your brain has not evolved to process information like a cyclops.

So when you see the split image in front of your eyes, regardless of what you may know about the device intellectually, your brain processes the information as if it was normal stereoscopic vision, because that's the way it's used to processing information.

That is to say, your brain "thinks" it's seeing two different images, and tells the rest of your body that "everything's cool, we can see like normal."

Because of this, you "feel" more comfortable--and more confident while wearing them.

But this is a false sense of confidence, because you do not in fact have the quality of information that your brain thinks you have.

This ultimately leads to more injuries and more struggles with movement--I have seen more people take spills, small and large, over relatively easy terrain using PVS-7s than I ever have with PVS-14s or BNVDs. This is because they feel more confident than they "should" be, and they process the information being given to them by their goggles as if it was stereoscopic vision, but it's not, which ultimately leads to more miscalculations, misplaced steps, etc. I've run full tilt into a ditch that I didn't see while wearing PVS-7s, it's not as though I haven't spent time under them--I learned to be a Platoon Leader using them.

Now, if you're moving slowly, over fairly familiar and uncomplex terrain, PVS-7s can be fine--for slow and deliberate movements like those of the Cold War Infantry, using NVDs to move to Patrol Bases or lay in ambushes in the woods, or defending a strong point, full well knowing that when shit "popped off" they were going to fire illum, pop the Claymores, and turn night into day, as conduct your assault/ambush without NVDs, 7s will do you just fine.

Where 7s begin to show their issues (again, besides simple size and weight, which ultimately we accept again when we decide to use true BNVDs) is during the much faster-paced, moving engagements that have begun to more typify Infantry engagements in modern operating environments--even moving through a city with something as simple as curbs on the streets present a much larger problem when you don't have any depth perception--but your brain thinks it does.

The thing that makes PVS-14s less comfortable for many people, and "harder to use" is in fact precisely what makes them "better," as they force you to learn a new way of processing information and your environment to develop a learned depth perception, but that once learned, is remarkably effective--whereas PVS-7s essentially allow you to "fake the funk" by tricking yourself into believing that the information you're receiving and processing is "normal," making them seem easier to use at first, but in fact putting you at a distinct disadvantage to someone using a PVS-14.

~Augee

I think you're confusing collimation with alignment.

Collimation in the context of dual tube goggles essentially means that the tubes are facing the same way--just like boresighted/collimated clip-on devices, most tubes have a certain amount of native shift to them as light comes in to the tube and then get spit out of the tube. Modern tubes are pretty tight--still not tight enough to be used as clip-ons without boresighting, but tight enough that it's usually not an issue.

What you're talking about is the actual physical alignment of the devices/tubes relative to the wearer's individual facial geometry.

What collimation addresses is the actual optical axis of the light/image being matched between the two tubes. Alignment being off is actually not a huge problem, as long as the tubes are collimated, because you're still receiving the image along a parallel optical track--it's like looking through the corner of a window instead of through the center--but you can still see the image through the window. Collimation is like if one window pane was bending light one way, while the other was bending it another. Un-collimated binoculars are kind of like being cross-eyed/lazy-eyed. If your left tube has a slight shift that moves the image up and to the left, while your right tube moves the image down and to the right, you can induce a bad "double vision" that your brain will fight mightily to resolve. If it's slight enough, you may not notice it consciously, but your brain will--which is what ultimately translates to eye-strain and fatigue during long-duration use.

~Augee