A recent thread about using a PVS14 while Trick or Treating and moving in and out of lit areas got me wondering about the Phokus Hoplite.

As I understand it the Hoplite works like the aperture on a camera lens. Depth of field is changed by using a small or large insert in the lens cover. This is how the Hoplite can give a focused image without adjusting from near to far. But the smaller apertures also restrict light.

So would one of the restricted apertures not also help protect the tube in a device without manual gain or gating? Maybe insert one of the smaller inserts that allows the device to be used in a fairly lit area. Then open the flap when in darkness and close the flap when approaching a street light or whatever.

It might not be specifically what the Hoplite was made for but I think it should work. I'd think even one of the middle sizes might help reduce light intake slightly to protect the tube.

Thoughts?

Actually that's a "middle class" solution.  The redneck engineering way is to poke a hole in a Butler creek #07.  It's not "autogating" but a manual "f-stop".  With the Hoplite you have a choice of "f-stops" if that's something you need.  I find a .225" hole works pretty good, both as a halo reducer and a re-focus ring.

in order to save tube in full moon nights, i bought an iris diaphragm and rigged adjustable aperture lens cap.
8...10mm opening is enough in full moon clear night.

iris closed (it does not close completely)



fully open

Exactly what I'm thinking the Hoplite will do although without the complete adjustability.

That would certainly be the cheapest option although without the convenience of merely flipping the cap open or closed.

Uh, yeah, that's exactly what I do with a Butler Creek.  It's a std obj lens cover, with a flip open cap.  The only difference between it, and a Hoplite, is the Hoplite comes with a choice of openings, although to get right down to it, for the price savings, you could get several BC caps and punch different dia holes in them for different apps, if that's important to you.  The Hoplite comes with it's own sacrificial window, but I don't know if that's readily replaceable.  I use a GI LIF any way (although a 30mm camera filter does the same thing for about 10 bucks).  So really, other than the nicer housing, and possibly better looks, the Butler Creek/ LIF mash up does everything the Hoplite does.

So when you hit a better lit area, you close the cover, leaving a .225" (or whatever) hole to see with.  When you clear it, pop the cover back open.  Like wise, if you need to read a street sign or whatever, flip it closed, so it focuses in closer, and then flip it back open to keep moving (with it set to infinity).  

While arguably it is doing the same thing as auto-gating, you are controlling the light entry manually, by "stopping down" the aperture.  This is a far cry from the tube doing it internally, if not automatically.  Even with auto-gating, I use this technique because it reduces the halo glare from light sources, and gives me a "re-focus" ring.  But there is nothing "auto" about it.  You are going to have to be johnny-on-the-spot, closing it down when required.

I would not recommend using this technique as "auto-gating" in a non-AG tube.  It simply allows the use of IR laser/illum in higher light areas, and allows you to read things closer up, without having to refocus the lens.

Or there is this.

Attached File

Duh.  Yeah, sorry.  Working off my phone and I missed the part about using a Butler Creek cap.  I read it as the standard rubber GI cap.

I know it isn't "auto gating" but rather just a mechanical way to limit the amount of light making its way into the device.

The Matbock deal would probably be the best of all worlds.  Twice the $$ but if it helps protect a $1200+ NV it should be worth it.

1.5 - 23mm iris diaphragm costs around $12 on auction site..

if you can make something that holds it in front of objective lens,you can save some money.

I understand that a mechanical shutter isn't going to protect the tube as well as or be as convenient as auto gating. Still I'd hope it would add some form of brightness protection even if not Instantly.

Yeah it will, but the OP is misleading by referring to it as auto-gating.  It would actually be something more like "middleclass man's manual f-stop and re-focus ring".  Although that doesn't have quite the same ring to it, that would be a proper description.  I would break it down like this:
Poor man's  f-stop/ re-focus ring:  Butler Creek #07 (modified)
Middleclassman:  Phokus Hoplite
Richman's: Matbock iris

I'm not trying to mislead anyone. I am just curious if anyone uses an aperture as a way to limit light rather than the advertised purpose of changing depth of field.

Not saying you are trying to do it mate, just that's the way the wording comes out, regardless of your motives.  It's the "auto" that's the problem here.  Maybe putting the AG in quote marks or something would show you are talking about a concept rather than the actual process itself.  People see that and automatically think of the internal processing going on inside the tube, rather than stopping down the light entering the front of it.  

To answer your question, yeah, my training partners and I do just that, with BC #07's.  I think the technique is fairly wide spread, judging from the comments in other threads.

I use the Butler caps as well, and find them to be very convenient.