Visual Purple

[x SF med]

12B, my one feeling is dented - "Wiseguy QPs"? Who would have ever thought? And if you notice it's us FOGs who are playing here.

FS - VP is an old term - and it relates to the physiology and the techniques of being able to see at night, without the use of starlight/ IR/ thermal assistance - us old guys used to have to rely on our (then) young eyes at night. If you just take a knee in the deep dark woods after you pass the wire, and allow your eyes to adjust (anywhere from 10-20 min) then remember to not focus directly at a target/objective, and keepo your eyes moving you can see pretty well at night - that's why red light is preferable - it does less damage to your night vision - because of the way the eyes process it, blue or white light does great damage to night vision. Why it's called visual purple, I have no clue, unless it's because if you mix red and blue you get purple...

[12B4S]

Damn, x_sf_med! Sure wasn't my intent to dent your one remaining feeling. Not to mention how surprised I was to see any comments from some 'Wiseguy QPs'. Yeah, I noticed it is the FOGs that are playing here. Another surprise.

You explained VP just as I remember it. At times, through the past decades, I still practice it. In some situations in civilian life, it is still a useful addition to one's sense of SA. There you go FS.

Seems like a good time to bring up 'rods and cones' and thier relationship to 'seeing'.

If QRQ comes across this thread, that's when are heads will start hurting.

[x SF med]

Ice Cream cones? It is about that time of year.....

I'm only a medic, and a bravo - I know nothing abut rods and cones - except something about a BAR.... (wiseass smirk)

[12B4S]

LOL.......... x_sf_med, not in these parts. It's 106 out there. Buy an ice cream cone, you best eat it inside.

Now you see!? We may need a 'wiseass smirk' smiley around here.

Rods and Cones, in FOGgy layman's terms. Just a 12B, I might add.

We use different parts of our eyes to see at night, then we do during the day. Rods and cones are cells that make up the retina. Cones in the center. Rods around the peripheral. We use the cones in daylight, which also gives us the ability to discern colors.

At night we use the rods to percieve any available or ambient light. So at night we are using our periphal vision more than we do in the daylight. Primarily trying to pick out shapes, shadows and such in various shades of gray and dark. It can be possible to look directly at something in the dark, in which case you would be trying to use the cone cells and not see it. This brings up another factor of using one's eyes and 'seeing', but by scanning side to side, one will pick up more in the dark by using your peripheral vision, because the rods are grouped at the sides of the retina and center cone cells.

Disclaimer:
Not being a Doc or Optometrist, I may have not quite explained the anatomy of the eyeball perfectly. It's about being able to use your vision to the best of your ability at night especially.

Now, time for the medics and experts to expound some.

One more thing. The Googling light is lit.

[x SF med]

12B - you guys got a cold front didn't you -only 106 in Scottsdale? Break out the Polypro!!!

Your explanation of the rods and cones is very succint and almost 100% - the other factor that affects direct vision at night is the optic fundus - the 'blind spot' caused by the attachment of the optic nerve to the retina - during daylight the effects of the attachment are mitigated by the alvailability of light and the fact that you naturally move your eyes around more - where at night - well you eyes get lazy and unless you conciously (or habitually) move them the lens of the eye tends to focus images on or near that area. cones still function at night - but since there is less color they do not work as well - notice how much differently you see with a clear full moon, than on a harvest or thumbnail moon (either wax or wane).

[12B4S]

Yeah. well. It had cooled off some at the time I posted that.

The 'blind spot' rings a bell, but wasn't aware of how it was caused. That is why at times at night, one can be looking at something and not see it. I'm not talking about a building or aircraft or something. I mean something small, as in somebody wanting to do you some great harm, a guard, and numerous other things, you would rather see and be aware of FIRST.

I went off and did the Google thing. Found a small explanation, that explains what is to me VP, in a bit more medical detail, yet not to make your head hurt.

"Rhodopsin is the key to night vision -- it is the chemical that the rods use to absorb photons and perceive light. When a molecule of rhodopsin absorbs a photon, it splits into a retinal and an opsin molecule. These molecules later recombine naturally back into rhodopsin at a fixed rate, and recombination is fairly slow.

So, when you expose your eyes to bright light, all of the rhodopsin breaks down into retinal and opsin. If you then turn out the lights and try to see in the dark, you can't. The cones need a lot of light, so they are useless, and there is no rhodopsin now so the rods are useless, too. Over the course of several minutes, however, the retinal and opsin recombine back into rhodopsin, and you can see again."

Working under a full moon, can almost feel like semi daylight. If on patrol or whatever, I always figured it to be a disadvantage.

Once again, the subject of eye movement comes up. As x_sf_med stated. Our eyes tend to get lazier at night and we develope 'tunnel' vision. If allowed to happen, you have lost any advantage. Perhaps for those that grew up hunting, it became natural. Most of us need to train ourselves to move the eyes, constantly scanning at night especially. It's amazing what you will pick up, what you will 'see'.

All you need to see or notice is not necessarily a full object or shape, a flash of a shape, a movement is normally what you will 'see'. With tunnel vision, you will miss it entirely.

I still practice scanning and eye movement off the balcony of the apartment. It looks over two other complexes. I don't miss any of the XX's coming and going. Practice, practice, practice.

[x SF med]

Brad-
Once learned, hard to forget or stop doing - esp driving at night.
Do I at least get a 40 yr old C-rat as a prize for taking this partially seriously, and raising the point of the optic fundus - which actually is placed differently, and sized differently in everybody (think retinal scanning for security)
If the snuffies, wannabes, and FNGs read this they might actually learn a little... dontcha think? Us FOGs actually know things!!

[12B4S]

True, x_sf_med. Don't think once learned we ever forget it totaly. Add to that, we more often than not do it naturally. However, even now, I do find myself at times having to conscientiously remind myself. Thing is, I do that in more of a Military fashion, as on patrol or op or training exercise. Damn! It would be nice at times if I could get the stuff in my head down through the fingers to the keys!!

Thing is. That just keeps honing an old skill that is in alot of ways, is just as useful in civilian life. One of the purposes of this thread, outside the fact that once in awhile old terms and skills are dredged up in my mind. Given that it is still taught in the Military, perhaps under a different term, it is valuable to every civilian and another weapon to add to one's SA arsenal.

I don't think we made it toooooooo 'head hurting'. As Peregrino posted toward the beginning of the thread. There is alot to 'seeing' and those more curious can reserach the whys, hows and workings of the eyes. I typed what I could remember. You added more and I learned more. Of course you just had to bring up the 'optic fundus' Medicsssssssss. Googled and learned a bit more. Thing is. This is just how it plain works.

Hopefully all those folks you mentioned and others have and will read this and learn something from the FOGs. I do think some have x_sf_med. One doesn't walk around the streets or wherever wearing NVGs.

LOL.... typical scrounger!!!! After all those decades of hauling that case of C's around, I forgot them in a space above the garage when I moved out of my house. However, I do have the remnants of one handy dandy, brown Accessory Packet. All that's left in it is the TP and the matches. Here I had that case, that I got back in Deutschland in 1970 at a Flintlock exercise at Hohenfels. I would have sent ya the Ham&MFs and Fruitcake. They were both in there. I aim ta please.

[x SF med]

I'll ytake the matches - they keep the bugs off. Why don't you donate the H&MFs and the Fruitcake to your local Al Qaeda branch - I'm sure they'd appreciate them.

[12B4S]

Done! The matches are yours. The address is a bit wide ranging though.

Great idea for the Fruitcake, Ham&MFs. Especially, when I don't give them the TP.