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  • illumination

    I as most of you know, am buying a USO scope with illumination. I have the choice of green or red illumination, now in my last post concerning this scope, someone mentioned using it in red, do to disruption of night vision. My question is if i set the green reticle at a low power is it still going to affect my night vision? Or should i go with the red. Keep in mind i really like the green. Thanks in advance.

  • #2
    Adam:
    Yes, the green will mess up your night vision, no matter how low you set it. Why? The eye builds up a chemical on the retina when you are in the dark, called "Visual Purple". which enhances nightvision. This chemical is insensitive to red light, which is why astronomers use red lights when observing. However, it is very sensitive to green light, because green light is the region where humans have the greatest sensitivity to light. So a little green light goes a long way towards wiping out the visual purple. Why are we most sensitive to green light? The peak wavelength of the Sun is 5550 Angstronms, which is, you guessed it, green. The Sun looks yellow because of the mix of colors in its spectrum, but it puts out most of its light in the green.

    Cheers,
    --Lee
    There are few problems a well-placed 308 cannot cure. --- Hawk

    Gentlemen! You can't fight in here! This is the War Room! --- President Merkin Muffley in Dr. Strangelove

    Rocket Science is much more fun when you actually have rockets! --- USN Recruiting Commercial

    A little revolution now and then is a good thing --- Thomas Jefferson

    Only the dead have seen an end to war --- Plato

    "In Ireland, in Lebanon, in Palestine & Berkeley, Patty Hurst, heard the burst, of Roland's Thompson gun & bought it!!!" --- The Late Warren Zevon, Roland The Headless Thompson Gunner

    In the 1500's, the Roman Catholic Church sold indulgences to forgive sin. In the 21st century, we call these carbon offsets. ---Hawk

    �Fight like a man, so you will not have to die like a dog� --- Calico Jack Rackham's Mistress

    Comment


    • #3
      "Visual Purple"[/b]
      aka rhodopsin

      Great answer, 'hawk.

      Red's the way to go. My IOR MP8 reticle is illuminated in red.
      www.precision-applications.com

      It's knowing that when I get up in the morning and my feet hit the floor, the Devil says, "Shit! He's awake!"

      Shortly before World War I, the German Kaiser was the guest of the Swiss government to observe military maneuvers. The Kaiser asked a Swiss militiaman: "You are 500,000 and you shoot well, but if we attack with 1,000,000 men what will you do?" The soldier replied: "We will shoot twice and go home."

      "There are so many Russians, and our country so small, where will we find room to bury them all?" - anonymous Finnish soldier

      Comment


      • #4
        WOW!! I just got blown away by tha tone. Great info, thanks for the help.

        Comment


        • #5
          Wow, I didn't know that. Very good answer, I vote this one goes to QandA section for future reference.

          Comment


          • #6
            Let me clarify one point, and add a bit more info. During the day, vision peaks at around 5550 Angstroms, and you see in color. This type of vision uses the "Cone" detectors in the retina. At night, in low light, your eye uses the "Rod" detectors, which peak at about 5070 Angstroms, or a bit more towards the blue. Also, you can see something much better at night if you look off to one side of it. This is because your rods are concentrated such that they are more sensitive to peripheral vision. Why? Because those of us in the past with good peripheral vision at night didn't get eaten by saber tooth tigers . Also, at night your eyes can only see in shades of gray, since the rods are not color detectors. Visual purple acts to enhance what light there is, which is why you do not want to wipe it out with a green reticle. I have read that some of the tunnel rats in Vietnam tried to stay in the dark ALL the time, to maximize their visual purple. However, after about 1 hour, there is no more appreciable build up.

            The size of your pupil changes too with increasing light levels. I think Chris from SWFA has covered this at length in another post, but just remember that you pupil will only open up to about 7 mm best case, for a young person. For us older farts, it goes down to 6 or even 5 mm. Thus, since the exit pupil of your scope is:

            Objective Diameter/Magnification

            It does NO good to have a scope where this ratio is greater than about 7, from the point of view of making the image brighter. Why? Because all that extra light will fall outside your pupil and not contribute to the brightness of the image. Where the lower powers are useful is when you need field of view for close-up work.

            Let's take the USS scope from SWFA as an example:

            4-16x56.

            So at the 4x end, the exit pupil is 56/4 = 14mm. Your pupil NEVER gets this large, so for this power, the maximum size the objective would need to be is 28mm.

            At the high end, 56/16 gives an exit pupil of 3.5mm, which is good for daylight use or twilight use.

            So you can see from the above, it's the higher power on a variable power scope that sets how big an objective you need.

            Also remember that your pupil is much smaller than 7mm during daylight... more like 2.5-3.5mm, so if you only use a scope in the day time, you should calculate the size objective you need accordingly. No, you will NOT be able to see more details in shadows with a bigger objective during daylight, because your pupil will still be closed down due to the ambient light.

            The eye is an amazing organ, with the ability to deal with a huge range of brightnesses. Here are some examples of what the eye can detect. The units aren't important, look at the range:

            # Starlight: 0.001

            # Moonlight: 0.1

            # Indoor lighting: 100

            # Sunlight: 10.000 (not looking directly at the sun, just how bright it is outside)

            That's a range of 10 million. Pretty cool huh?

            Cheers,
            --Hawk
            There are few problems a well-placed 308 cannot cure. --- Hawk

            Gentlemen! You can't fight in here! This is the War Room! --- President Merkin Muffley in Dr. Strangelove

            Rocket Science is much more fun when you actually have rockets! --- USN Recruiting Commercial

            A little revolution now and then is a good thing --- Thomas Jefferson

            Only the dead have seen an end to war --- Plato

            "In Ireland, in Lebanon, in Palestine & Berkeley, Patty Hurst, heard the burst, of Roland's Thompson gun & bought it!!!" --- The Late Warren Zevon, Roland The Headless Thompson Gunner

            In the 1500's, the Roman Catholic Church sold indulgences to forgive sin. In the 21st century, we call these carbon offsets. ---Hawk

            �Fight like a man, so you will not have to die like a dog� --- Calico Jack Rackham's Mistress

            Comment


            • #7
              Hawk,

              Yes it is pretty cool. I think it has been 4 decades since I have heard the word Angstrom. Excellent coverage of this topic.

              HB
              Today, what goes up does not have to come down!

              Comment


              • #8
                There are many, many reasons why, several covered above, but trust us... go with red.
                You don't want to pay that much money for a scope, use it for a while, and decide the green reticle isn't what you thought it would be. It looks cool I suppose, but red is a much more effective and functional color for low light illumination.
                On the other hand, if you're only going to be using it for moderate "LOW" light situations, such as early morning/late evening varmint hunting or the like, and mainly daylight "range" use other than that, and you just want an illuminated reticle because you and your buddies think it's kind of cool, then it probably won't matter which color you choose. For real life tactical or "critical" work however, red is the only real choice short of a true night vision optic.

                Just my .02
                "We stand at the ready at Hell's front door. We are the sharpest, and most potent arrow in the quiver of last resort and upon us hangs the weight of being the final option. When it cannot otherwise be done, we are called. When lives are at stake and the specter of death roams freely, we are put into the fray. We go once more into the breach where others fear to tread. We do what others won't, or can't, and we are allowed no errors. For us mistakes mean death. We must train as if our lives and the lives of others hang in the balance for indeed they truly do. Spend this day and every other seeking perfection in the warrior arts."

                Comment


                • #9
                  As the color of lights relate to night vision, there are varying opinions as to what is best. For a very good coverage of night vision try the URL below. Although not totally related to the illuminated reticle, it does a good job of covering light colors and eye capabilities. For chosing a color of reticle illumination, I would go with the guys that have and use them, they know best so reference the above comments.

                  http://stlplaces.com/night_vision.html

                  HB
                  Today, what goes up does not have to come down!

                  Comment


                  • #10
                    What the author above doesn't take into account consistently is the sensitivity of the eye. The rods are much more sensitive to green light, thus, for the same absolute illumination level, a green light will look brighter than a red light. This in turn will more quickly turn off rhodopsin regeneration in the case of red than green light. He almost has this conclusion in his text, where he states "it's not the color, but the absoulte intensity that matters". Well, to the human eye, green appears brighter than red. It is not a "myth" that red light helps preserve dark adaptation.

                    Regards,
                    --Hawk
                    There are few problems a well-placed 308 cannot cure. --- Hawk

                    Gentlemen! You can't fight in here! This is the War Room! --- President Merkin Muffley in Dr. Strangelove

                    Rocket Science is much more fun when you actually have rockets! --- USN Recruiting Commercial

                    A little revolution now and then is a good thing --- Thomas Jefferson

                    Only the dead have seen an end to war --- Plato

                    "In Ireland, in Lebanon, in Palestine & Berkeley, Patty Hurst, heard the burst, of Roland's Thompson gun & bought it!!!" --- The Late Warren Zevon, Roland The Headless Thompson Gunner

                    In the 1500's, the Roman Catholic Church sold indulgences to forgive sin. In the 21st century, we call these carbon offsets. ---Hawk

                    �Fight like a man, so you will not have to die like a dog� --- Calico Jack Rackham's Mistress

                    Comment


                    • #11
                      Hawk,

                      Your are absolutely right and I agree with you. I just like to play devil's advocate once in a while. You can be sure all of the submariners know what red is and how it works. Thanks again for YOUR coverage since it awakened some long forgotten words and lessons for me.

                      HB
                      Today, what goes up does not have to come down!

                      Comment


                      • #12
                        For those that might read this conversation after the fact I thought I would throw in something of value. Before I sent a lit reticle system to a buddy in a war zone I looked through the scope from the perspective of the target. You can recreate this experiment by benching the scope and focusing it on a target about 50 feet away. What you are sighted in on is almost as important as being sure the gun is empty if the scope is still attached to a weapon system. Go to the target you are sighted in on and look back at the scope. If your eyes are close to the aiming point you will notice a glowing area from the lit reticle system. Perhaps this is subject to only a few brands of scope(I have not had the oppertunity to test them all) but most humans would notice a red stoplight looking back at them from the darkness. This red light is not a big deal to a coyote or paper target, which is probably what most of these scopes are looking at, but for the LE and MILITARY this is a severe limitation to the lit reticle system that those shooters should be aware of. Sorry if I have insulted your intelligence by mentioning this. See ya


                        Mike

                        Comment


                        • #13
                          Just adding one more fact to Hawk's excellent technical knowledge.

                          Night vision is much much better if you don't smoke. The carbon monoxide really messes up night vision. Ask any pilot. Smoking and altitude takes out your night vision

                          Dihedral

                          Comment


                          • #14
                            You can lose up to 45% of your night vision by being a smoker (this depends on many factors).

                            Smoking inhibits the bodies production of rhodopsin, which is the chemical in the eye that helps ya see at night.
                            www.precision-applications.com

                            It's knowing that when I get up in the morning and my feet hit the floor, the Devil says, "Shit! He's awake!"

                            Shortly before World War I, the German Kaiser was the guest of the Swiss government to observe military maneuvers. The Kaiser asked a Swiss militiaman: "You are 500,000 and you shoot well, but if we attack with 1,000,000 men what will you do?" The soldier replied: "We will shoot twice and go home."

                            "There are so many Russians, and our country so small, where will we find room to bury them all?" - anonymous Finnish soldier

                            Comment


                            • #15
                              A single color of light in the quantities that we are talking about will not significantly wash the rhodopsin or iodopsin of the eye, nor will it take any any real noticeable time to regenerate it. At worst case a minute or two. Full spectrum lighting is what kills the rhodopsin faster than anything, such as bright sun light or snow fields. Even brief encounters with bright lights at night will not significantly impact dark adaptation. Dark adaptation takes about 45 minutes to implement on an eye that hasn't been overly washed out. To reduce this time, pilots used to wear red goggles for an hour before flying to reduce the adaptation time. While it worked somewhat, it wasn't worth the hassle and it was dropped. Also, flying with night vision devices doesn't use the Scotopic vision with the rods, but the day vision with the cones, so dark adaptation isn't as necessary as it used to be. Interesting fact. When wearing NV devices for a long period of time, when taken off around any normal lighting, you will see everything in a purple haze for about one minute until the Iodopsin of the eye is regenerated.
                              If an individual is in the field, as long as he doesn't stare at the setting sun, the mesopic phase of vision will be sufficient to allow dark adaptation without any problems. The problem that the shooter is going to have is that he must use the fovea centralis which is primarily day vision to use the reticle. It situations where the light is so dim that the shooter has had to dark adapt, he will have a problem seeing the target as off center viewing isn't an option when looking through a scope. The eye will naturally drift towards using the day vision to see the reticle and then the target will wash out. Therefore, reticle color in a Scotopic world is the least of ones problems, it is overcoming the use of the fovea centralis. I have tried to night shoot with a scanning pattern with a unlit scope and haven't been able to get it to work with any success. Using the heavy posts to bracket the target doesn't give enough accurace to hit anything repeatedly beyond about 50 yards. My conclusion is that if you want to shoot at night (true dark) then you need to invest in a scope that will allow you to use day vision, hence a NV scope such as a Raptor or some sort of thermal scope. Now, for photopic or mesopic vision, then I agree with everyone else, stick with the red as green on the low settings tends to blend with the earth tones better, and while more visually appealing to our eye, then takes more effort to see.
                              One question I have, what do red/green color blind people see when looking at a illuminated reticle? One last thing, altitude also effects the ability to see as the eye is a very oxygen dependent organ, so if you are going to shoot or move at altitudes that you are not used to, you had better altitude adapt as well. Military snipers in Afghanistan that are going to work high altitudes have been known to carry small medical oxygen bottles and masks to pre-breath once they get to their hides to get their eyes up to par.

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