The left tube (both WP filmless) on my binos I can't seem to get as optimally focused at distance compared to the right tube. Both objective lenses are set the furthest away they can get. When I close my left eye, a tree line about 80 to 100 yards away looks crisp. When I close my right eye, the tree line is just a little bit blurry. Messing with the ocular focus doesn't seem to really do much. I also am not an expert and maybe I'm missing something. It seems like my left objective focus, if it could go just a little further would be perfect, but it's maxed out just short of where i'd like it to be clarity wise at distance. I just thought it was odd since the right is perfect. This is when wearing contact corrective lenses.

Any tips from the pros?

We were alway taught to cup our hand over the tube that we weren’t focusing and then adjust the adjacent tube. The thought is that when you close your eye it can cause some slight temporary distorsion to your lens in your eye since it is somewhat flexible. Don’t know if someone else has a better more high speed way or if it’s mechanical.

What are the specs on the tubes?

I have dual pvs-14’s. Both have very good specs but one has a tad better specs. The other tube simply isn’t as clear. I thought it was focus too. It wasn’t.

Keep in mind that even if they have the same specs the image could be just a bit different.

Or there could be a small smudge on the inside of one of the lenses from assembly.

Could be several things really.

this is how to do it

if that doesn't work, it might be broken

When is the last time your eyes got checked ?

If you try focusing on stars (or some pinpoint light source decently far away, say 150+ meters), does the left objective lens focus in a manner that first the stars are blurry, then it gets better and better, until it flips and starts getting worse again? Meaning does it go past the infinity point? If that does not happen then you have the infinity lock ring set too close and you need to screw it away from the lens a bit.

Just to be clear in case my explanation / question is worded poorly:
- close your right eye (or hold your hand on the right lens to block it for reasons mentioned in this topic)
- focus the objective lens as close as possible (leave eyepiece wherever doesn't matter)
- start turning the focus to the other direction
-> the blurred stars start getting smaller, the blurry blob I mean
- at any point when focusing further away, do the stars suddenly begin to get blurrier / bigger blob?

If yes then the problem is not directly in the focus range, if the answer is no, then it's most probably just the infinity lock ring and you need to adjust it.

Edit: as a sidenote I don't especially enjoy using the infinity stop rings, I have them screwed some good amount further than they need to. Then I will always have the proper range to get infinity focus instead of having the ring move slightly and messing the focus range. The plastic ring is too soft I feel and even if I adjust it "perfectly" it still depends on how much force I use to rotate the objective lenses whether it will actually stop at infinity, or just before, or slightly after (and then everything is off focus). Maybe if I glued it down it could be a bit better.

And as a second sidenote, the coarse threading on the objective lenses is not exactly the most user friendly regarding infinity focus or any precise adjustments for that matter. It is durable so that's great, but for example with a MUM it is so much easier to adjust focus with precision. The threading on a MUM is so fine that it's lovely smooth & precise, though it is easy to cross thread.

Maybe I mis-read you murtis but did you mean to say "OBJECTIVE" lens in your post. Usually the lenses on the front of binoculars are non-adjustable.

Usually the "OCULAR" lenses at the rear of binoculars are the adjustable ones. Not trying to be picky, was just a bit confused.

According to the web, right eye dominant people are about two thirds of the population.

Perhaps that is why binos have an adjustable left ocular lens and the right lens focus is done by the center focus wheel. Also the weaker eye's image is "blended" in the brain to create a uniformly focused image, IN MOST CASES.

OP, as someone mentioned, maybe an eye exam is in order. It is possible that your corrective need is beyond the ability of the bino's range of focus. Take the binos with you to the Dr.

Lastly, you can get some distortion through the binos if the pupillary distance is not wide enough to place the optical centers of the lenses in front of your respective optical centers of the eyes. Look on the web for a definition of "pupillary distance".

I have trouble finding glasses frames large enough to fit my PD of 72mm. (fat head)

You have a objective lens lock ring which needs adjusting to let it focus to infinity for your eyes. It’s located behind the objective lens and has a very tiny Allen screw on it that you loosen and adjust ( turn ) to let you be able to adjust the objective lens.

Goddamit arfcom, there ya go makin me learn shit I didn't know about. Will have to check out my admittedly older German binos to see it they have it.

While we're on the subject of focusing, can I ask a related question about the diopter focus?  The indicating dot and the scale on mine (MOD3-B) are nowhere CLOSE to aligned.  Between 90-180 degrees off for each eye.  Is there a way to fix that?  Also, is it correct that the diopter is more or less a "fine focus" to the infinity focus ring's "coarse focus"?  Or are they two very separate things and need to be focused independently?  If so, what's the best procedure for that.  Currently I use stars to infinity focus and then try to fine-tune with the diopter.  Also anyone know what size allen key to use for the set screws on the MOD3-B infinity stop rings?  None of mine seem to work, so I have been unable to adjust the left eye fully since it's firmly set.  Nor lock down the right when I have infinity where I want it.  Of course I keep having to re-adjust anyway, because like someone else mentioned I've noticed the stop is pretty damn soft and can 'shift' each time I focus.  Which I tend to do a lot as I keep re-focusing for close up to read signs or take a look at the ground near my feet, etc.

Yes objective lenses. Both are adjustable in a NOD that uses PVS-14 style otics. Or pretty much everything else too. The objective lens is just a simple screw in lens cell in one part that moves in & out and adjusts front focus. It has to as the aperture is so huge.

Oculars are adjustable also, like in a regular bino too.

There is a way, but it is by no means necessary or needed. You will be adjusting them from time to time anyway as they move pretty much by themselves while putting into storage etc.

And no, it's not a fine focus, it's a correction for your vision pretty much, or to be more precise it moves the image plane you see closer / further. If it is set properly at 0, the image should be at a distance of infinity, like stars are.

The procedure can be found from the PVS-14 techical manual TM-11-5855-306-23-P and is found everywhere around the net.

You will lose collimation though if you rotate the whole eyepiece assemblies. Assuming that was done in the first place, and it is still in that same state. But like said it really doesn't matter what the numbers show and not all NODs have a numbered diopter scale.

@murtis

If it’s the lock ring being too close, Is this a simple fix/adjustment I can do myself without messing up the purge or the tube in any way? This would be on a MOD3.

It is and no possibility for messing the purge, assuming there is anything but regular air inside anymore.

The lock ring can have a set screw (0.05" hex) holding it in place or it can be glued, or even both. Usually if it's glued it's still meant to be adjustable so the glue should crack easily. I haven't touched one with glue in it, but knowing the lock ring is brittle a spanner tool made to grab the little holes would be the safest bet if it's really tight. Normally it's enough to grab it as evenly as possible with your fingers making a circle around it, but for the glued ones I can't say for sure.

When you get it loose, then just readjust it, or just screw it in as much as it'll go so it'll never bother you again.

Same procedure for anything that uses a PVS-14 optics. Now thinking you didn't mention if you have ANVIS objective lenses (not sure if there's even a MOD3 model that accepts them) but if you do, then the procedure is different. It is the same idea, but as I have so little experience with ANVIS optics I'd rather leave this then to someone else. If it's ANVIS then I'm sure someone else will fill in, but the basic idea is to loosen the objective lens and then you can rotate the infinity stop to a different position to allow proper focus. Then retighten.

Either way no need to break the purge seal.

Thanks! Unfortunately I don’t have a small enough hex key to loosen my set screw right now, but once I get one this should fix my issue!

Got ahold of a .05” Allen key and it’s still too big!

i think the size is 0.035 inch - not many key sets go that small ,

Sorry.. Johnelot one post up has tons of more experience, I'd trust him more too

Objective lenses should focus past infinity.

If you are hitting the focus stop either the focus stop is in the wrong position, or the tube is not seated all the way.

Start with the focus stop (as discussed above)

Thanks for the help everyone. As discussed by several it was indeed the focus stop ring stopping my ocular adjustment just short of where my left eye needed it to be. Once I finally got a .035” Allen key to move the set screw it was easy-peasy. Thanks everybody! Now I can get full performance out of this 36 SNR filmless WP tube

Are you a dual tube system where you can turn off each tube?

If so:

1) Go outside at night. I know, it's scary.
2) Hope you have clear skies, if not, just give up.
3) With both tubes off, look up at the sky, preferably with your mouth open and tongue hanging out in that legit "herr derr I'm an operator" expression we all get.
4) Turn on left tube.
5) Adjust front spinny thing to infinity, the blurry dots in the sky should be smaller in that direction. If they get bigger you're going the wrong way.
6) Now turn the rear spinny thingy until the blurry sky dots become crisp sky dots.
7) Turn off left tube.
8) Turn on right tube.
9) Repeat steps 5 & 6 for right tube.
10) Turn on left tube.
11) Use front spinny things to adjust focus closer than the sky-dots.
12) If you succeeded, eat a hot pocket. If things are still FUBAR'ed, repeat entire process, making sure you hold your tongue in a more awkward position this time. Failing that, make an appointment for eye exam, CAT-scan, or if all else fails warranty work on your NODs.