Friday, November 28, 2014

Night Vision

Mk 1 Human Eyes

“Don’t get a light that’s so bright it blinds you, kid,”  the elder said to me one night over beers.  “You want a light that saves your night vision, just enough to let you move through a dark basement at night.”

We learn from experience, but nobody says we can’t learn from other people’s experience.  That is the definition of wisdom and the foundation of an education system.  But that doesn’t mean we should take everything on face value either.

How bright should a tactical flashlight be?  One school of thought says as bright as possible.  You want, they claim, eye-searing, sunburn-causing, uber-bright light that make the VCA (violent criminal actor) blind and cringing in fear.  Faced with that hype, other manufactures with less bright lights have retreat to claims about run time, size and functions.  It’s all marketing.

I haven’t heard one manufacturer advertise a tactical light that preserves your night vision. 

Illumination
Let’s for simplicity define a lamp as anything that produces visible light, no matter if it’s a bulb, diode or carbon arc.

Lumens are a measure of the total light output from your lamp.  It doesn’t matter if the light falls on your subject or goes sideways into space.  It’s total output.  This might be the best, simplest way of comparing flashlights.

Many lights are advertised in watts, an expression of the rate of energy flow/transfer/conversion.  The power company speaks of kilowatt hours, or the energy consumption per hour they have to produce.  The problem with watts is efficiency.  A lamp rated at 3 watts at 80% efficiency produces 2.4 watts of light.  But a second lamp rated at 4 watts but 40% efficiency only produces 1.6 watts of light.

Lumens are a better comparison value.

While lumens define total light output, it doesn’t describe the amount of light shined on a surface.  That moves us to footcandles and lux.  These are measures of the amount or density of light that falls on a surface.



tactical light night vision
There was a time when specifically constructed candles were used as a standard of the amount of light thrown on a concave curved surface one foot away.
Imagine each of the fundamental particles of light, the photon, is a gumdrop.  If you put 1000 gumdrops on a the cover of a phonebook, people would say that’s a lot of gumdrops, but take the same 1000 gun drops and spread them out on a football field.  Not so many gumdrops.

That’s why measurements of light on surface usually have a value of some specific area buried in the definitions.  The light on a surface is luminance and is measured in footcandles or lux.  I prefer footcandles.

Are we there yet?  Someone in the back row has an inquiring mind.

No, not by 700 rows of cherry trees.

Imagine two walls in the same room, one is black and the other is white.  Which wall will reflect more light back at you?  The white wall has higher reflectivity and more light will enter your eyes so you can see it better.  The black wall doesn’t reflect so great.

So is my drinking buddy still sounding good to you?  Frankly, I’m sure you could design a light that would illuminate a specific area and not disturb your night vision, but outside of that specific location and conditions, the lamp would be useless.

The eye is our sensory organ for vision.  This complex biological structure converts photons of a specific range of colors to electrical signals the brains interprets as vision.
Of all the parts of the eye (cornea, iris, optic nerve, fovea, blind spot, rods, sclera, cones and all the rest), I’m only interested in rod, cones and fovea.

Night vision
This is an SEM image of rods and cones from an eye.

Each rod and cone is sensitive to a single photon of light.  Pretty amazing isn’t it?  The major difference between night vision and day vision is in inhibition, convergence and how the rods and cones are hardwired to the human brain.  The amount of photosensitive pigment available is also an important factor.

Combination of these four factors determines which mode the Mk 1human eyeball operates in. The modes are photopic, mesopic and scotopic.  Let’s deal with the first and last.




Photopic
Scotopic
Photo receptor
Cone
Rod
Sensitivity to single photon
Low
High
Acuity
High
Poor
Color perception
Full
No color perception

We refer to photopic as day vision and scotopic as night vision.

One can’t help wonder if the test of night vision would be to take a color chart with you and if all the colors look gray you are either fully color blind or are in night vision mode.

When there is a lot of light available for photopic vision, the cones and rods create lateral inhibition by decreasing the sensitivity to light.  That’s an edge sharpening effect.  Since our vision is highly dependent on contrast, edge sharpening does the same thing your camera app does.  It throws away light to make the contrast between objects sharper.  Since there’s plenty of light available, who cares about wasted light?

As the amount of light decreases the eye/brain decreases inhibition and begins convergence.  Convergence causes the rods and cones to sum their signal to the brain instead of reporting individual signals.  The immediate effect is loss of visual sharpness.

As the amount of light decreases, color perception changes as your cone contribute less to the image.  Cones are tightly packed at the center of the eye’s fovea, but both rods and cones have a distribution though out the eye.  Rods dominate the peripheral of the eye.  You’ve experienced that effect when an invisible object become noticeable seen at the edge of our field of vision.   When the cones no longer function the fovea becomes a blind spot and no image can be formed there.  A practical concern for laser safety officers is preventing laser damage to the fovea which would drastically reduce your daylight vision and could make you permanently and legally blind.

We often equate scotopic rod vision with night vision.  That isn’t true, especially in urban environments where there is enough light to prevent true scotopic vision.  Our eye’s work in these cases in a mixed mode of rod and cone vision called mesopic vision.  It’s complicated.  Too complicated for this walk in the woods. 

Table one shows levels of illumination expressed in candles per meter squared and typical sources as well as transition levels between visual modes.

Table one, in footcandles per square meter

So what’s a lumen in units of Cd/m2?  Beats me.  You need to know too many other variables but the thing to note is the transition between photopic and mesopic is around 3cd/m2 or a little past sunset.  Surely your lamp throws more light than that.  

Each lamp has a different angle in which it spills light.  That angle will affect how much light will fall on a square inch at any distance.  Smaller angle more light, larger angle, not so much light


True total night vision requires less light than a moonless night in the lampless woods.  Do you really want to use that level of illumination, and all the limitations of poor resolution, low contrast and no color perception when you need to determine if that’s a phone, wallet or semi-auto in his hand?

So no, I think my drinking buddy has had too much to drink on that subject.  I suspect you want to operate in low levels of photopic or upper levels of mesopic vision mode.  But it isn’t all about light levels; it’s also about transitioning between levels.

Mythbusters did a program on why pirates wore a patch over one eye.  Their answer was that one eye would be dark adapted when they go below deck into the darkness of the ship’s hull.  I think the loss of stereoscopic vision on a moving deck would be a poor trade for one dark adapted eye.

Dark adapting.
Rods and cones contain light sensitive chemicals called photopigments.  There are three basic types which give us the range of color sensitivity we enjoy.  Light changes or degrades these molecules which produces the electrical signal the brain needs.  It’s the speed that these pigments regenerate which effects how fast we dark adapt.

The rate at which rods and cones regenerate is different.  Cones (color vision) regenerate faster than rods.  In absolute darkness, cones take about 5-7 minutes where as rods take 30-45 minutes to reach in normal eyes, full dark adaption.  Cones however do not have the same level of sensitivity as rods.  Rod will take longer, but reach a higher level of sensitivity of dark adaption.

Roughly speaking, depending on pre-dark adaption, it could take 30 minutes to reach 80% of full and complete dark adaption.  Of course the eye is expanding the size of the pupil to accept more light and the cones and rods are converging to produce a stronger signal.  80% isn’t bad.

Let’s look at the other side, going from dark to light.  All that adaption can be lost in a second of exposure to bright light.  Exposure to the illumination level of a neon lamp is sufficient to lose total dark adaption and suffer flash blindness. 

Flash blindness is visual impairment during and following exposure to a light flash of extremely high intensity.

Want to weaponize your flashlight?  You just need a light as bright as white paper in a good reading light. When you shine it into someone’s eyes your target will be blinded.  Turn it off and if the general illumination level would support lower mescopic or the upper part of true night vision or scotopic, your target will remain night blinded.  

But you’ve got to get it in their eyes, in both eyes and remember the level they are exposed to will influence how long the effect will last.  Even so, gaining 2 seconds on a VCA is a tremendous tactical advantage.  So use a little more light and get more flash blindness and time.  Flash blindness, however, isn’t a paralytic condition that immobilizes the exposed person
.
Also note the light is being reflected back at you, so the more you use, the more your dark adapted mesopic or scotoptic vision will suffer. 

Did you catch that part about pre-dark adaption?  Simply put, spend a day in full sun on a sandy white beach and it will take longer for your eyes to dark adapt when you walk out of the sun and into a dark basement as if you spent the day inside with the shades drawn.  

night vision
This officer is wearing both a brimed cap and very dark glasses.  Her back ground suggest she works in a very bright area.
You can improve the process by wearing, neutral gray sunglasses with side shields that decrease all wavelengths to a 15% transmission level.  Wearing a cap with a brim also helps.

Tactical considerations
Pre-dark adapt whenever possible. 

Accept that in the city and many rural areas you will never be fully dark adapted, so going from yard lit with a security light to an unlit basement will be a problem.  If possible, get out of the doorway so you’re not backlit and move to an area of relative safety to allow your eyes to reach a better level of adaption.

A weapon light with two levels has some advantages in different situations, very bright for distances in the open or for causing flash blindness and a lower level for maneuvering indoors and identifying people and objects.  You must master these controls at the unconscious competency level.

Remember flash blindness is a two way street.  Light decreases by the inverse square of the distance (double the distance and an object receives only a quarter of the light it would receive if it was at the original distance).  So the light in the VCA eyes will seem 4 times as bright as it does to your eyes.  In most cases it will still be bright enough to alter your level of dark adaption.  Pick you light with at in mind.

At night or in a darkened room a very bright, focused light illuminating a 4 foot circle on wall will create very dark, concealing shadows two feet past the edge.  Your vision, no longer dark adapted, will be photopic from the ultra bright light reflecting back into your eyes.  You will not be able to see well into the inky dark shadows further down the wall or in corners of the room.  Think of this as a form of tunnel vision and correct for it by:

  • Expanding (refocusing) the area illuminated to see more,
  • Selecting a less brilliant light,
  • Working with a partner who has the responsibility to check the shadow.

The best way to select your flashlight is to try one or three.  Get a buddy and find out what the light does at to him at difference distances.  Let him flash blind you with it and find out what you can see and for how long.  Run the experiment on him and find out what happens to your vision.

We buy flashlights to see in the darkness.  One can only imagine the influence nightfall had on early man as familiar objects disappeared outside of the limited area of safety a campfire produces.  Learn to control your flashlight and you can rule the night.

Personal note:  I’ve been running a few experiments about light and vision.  When I’m truly dark adapted I can’t see colors.  Some fade into the ones next to them and are indistinct.  Others appear to be different levels of gray.  My visual acuity under these conditions stinks.   I’m not sure I could identify a threat hiding from me with scotopic vision only.  I need more light.

When I use my 150 lumen light and I’m truly seeing only grays,a flash of illumination to check a tight corner by a wall in my basement creates enough reflected light to blind me and makes my eyes spasm in pain as the dilated pupils slam closed to reduce light.  

I’m momentary blinded while my eyes rapidly move from scotopic to photopic vision.  During this instant I am truly blinded.  While this occurs and is actually worse for the VCA, he only has to unleash a barrage of un-aimed fire at the light and hope one of the rounds connects.  As the law abiding citizen (cops, too!) we don’t have that option. We must identify the threat first.


I suggest you don’t waste your time waiting for scotopic or true night vision.  It’s too easy to lose and takes too long to recover.  Try to stay in mescopic vision. It’s a wide range of vision, fast to recover and gives combination of color and resolution you need.  

Sunday, November 23, 2014

Different Worlds

As I type this Akron Police Officer Justin Winebrenner has just been laid to rest, not far from my home.  By all accounts he was a good man, a man most of us would have been happy to know.

Sunday morning, Nov 16 2014, around 2:00 he was at Papa Don’s Pub with his future wife (whose family owns the bar) and a buddy, another off-duty officer.  Justin was previously at an athletic fund raiser at another location.
  
I don’t have all the facts, only what I can pull from the newspaper and news sites, but at some point Kenan Ivery created sufficient trouble that he was asked by the bar to leave.  He did, but only long enough to retrieve a gun and return to the bar brandishing it.  

At this point unarmed and off-duty Winebrenner felt he had to get involved.  Ivery discharged his gun killing Justin and wounding four other people.  Unfortunately, Ivery was later taken alive hiding in a nearby railyard. 

That’s the stripped down fact picture.

I was stuck in traffic the following Monday and tuned in the local talk radio station hoping to find out the cause and extent of the traffic snarl. Predictably the topic was Justin Winebrenner.  The caller just couldn’t believe anyone would just walk into a bar and open fire.  I understand his problem.  He’s ignorant, never having to deal with the dark side of society.

Surely, the caller explained, there must be some reason, some connection between the two men, some fact that would act as a compass and guide him to some kind of understanding.  The caller couldn’t find any reason that made sense.

I’ve talked to men who worked the county jail.   Typically the prisoners are people waiting for trial, or serving short sentences.  The jailers walk around unarmed with the exception of a radio with a panic button. 

I couldn’t help but wonder if this wasn’t dangerous.  It was explained to me that most prisoners believe that good behavior in jail while waiting for their trial would benefit then at sentencing.  But I’ll never forget what one officer of them told me:

“There isn’t a person in here that wouldn’t shank me if they thought it would be to their advantage.”

If you’re a civilian with or without a CCW permit you need to realize most criminals operate with a total different mindset then you and your buddies.  They will do whatever they think will benefit them that instant without any real thought to future events.  

I had an instructor tell the class about a mob man, a contract killer, who thought TV police dramas were a hoot.  
“See, you cops have to worry about where your rounds go, I don’t.  I’m just going to empty the gun and hope I hit something I want to hit.”

That sounds like Ivery, doesn’t it.  I can’t find how many total shots were fired.  We know he hit 5 people.  It doesn’t sound like he had an escape plan.  Google maps showed the railyard was two doors down.
  
I can hypothesize why he returned with the gun and why he decided to shoot Officer Winebrenner and why Officer Winebrenner was unarmed but that’s all meaningless for this blog.

Here’s what I get out of this tragic event.

There are few safe places where you can be in condition white.  So don't be in condition white! 

Criminals will act for reasons that make sense only to them so you must always be prepared.  You should never think “Nobody would hide behind a car and just empty their gun at people walking to another car!”  You should be thinking “If someone hid behind a car and just emptied their gun at me or other people what would I do?”

Alcohol and guns never mix, so make the decision to be sober and armed. 

People will do bad things, create horrible acts and awful outcomes to solve problems that they created for themselves.  So your thinking should never be “nobody would ever do that...” but rather “if someone does that…” 

Lets go to different world.

Ferguson, Missouri
We’re still waiting for the grand jury to announce their ruling on the shooting of Michael Brown by Officer Darren Wilson.
Papers report gun sales are increasing and people with their own agendas are arriving in town almost hourly.  It sounds like a IED with a slow burning fuse.

Read Chris Hernandez’s blog.  He’s one of my favorite bloggers, I mean outside of myself.  I like him because he appears to be open-minded and honest about his opinion.  He’s done a spectacular job on Ferguson.

I followed his link to Tumblr and I was horrified by the results. 

Clearly massive, organized rallies have been organized in states across the nation.  These events are outcome independent of what the Ferguson grand jury does.

I believe in the right to peaceful protest.  And these rallies maybe organized as peaceful, but any organizer who did not account for violence is naïve at best and dup at worse.  I do find it interesting that Tumblr doesn’t list the person who created the site.

I expect violence in any case.  We’ve seen mobs loot and burn because their team won or lost the big game.   After all this time, with people stoking the fires of indignant morality, helped by the mainstream media who constantly remind us about the power keg in Ferguson, don’t you think there won’t be a spark which will be fanned into a flame by the rhetoric?

And it isn’t just going to be in Ferguson.  Passions are inflamed and rallies already planned, maybe in your backyard.

Remember the truck driver Reginald Denny who was pulled out his truck during the 1992 LA riot sparked by Rodney King.

The poor man was just trying to make a living , had nothing to do with Rodney but was in the wrong place at the wrong time.  As I remember it, he slowed down as not to run the rioters over which enabled them to pull him from the cab.  

I wish I could give you guidelines.  My thoughts run to:  the members of the mob share the lawlessness of the few, or if you’re right to shoot someone, you’re right to run them over.  

I wish I could impart how to do this with car, truck or van by flashing it’s headlights and sounding the horn while slowing accelerating until you’re clear.  

I wish I could tell you that you can only defend property with lethal force if the property is occupied by innocents.  In any case remember who calls the police, typically victims and innocents.  Get somewhere safe and make the call.

You want to carry a gun?  Are you expecting the zombie horde and are a survivalist?   You should know this shit.  You should know what reasonable force is and how to determine when it is justified. 

I never expected to see this kind of organized, potential violence in America.  Just because your town isn’t on the Tumblr list doesn’t mean the knuckleheads aren’t stopping by.
  
Keep your wits about you and your tools close at hand.

PS:  25 Nov 15

Grand Jury announce Monday night......


Nothing says I demand social justice like looting a liqueur store!

Looks like they could have uses a few Korean store owners and a couple 12 gauges! 



  

Wednesday, November 5, 2014

Printable Guns - Update

More plastic guns

Up date on printable guns.  Read the original post here.

 Michael Crumling has come up with one solution for the fragile nature of printable plastic guns.  He’s a 25-year-old machinist and has developed what amounts to a disposable barrel with a live round in the chamber.  It’s expensive and time consuming to make, but it turns a novelty item into a functioning weapon.

His other idea?  Why not use non-regulated metal parts like triggers and firing pins?

It’s only a short step until someone finds commercially available high strength steel pipe with an ID that matches a common pistol round.

Printable guns are an example of technology getting ahead of society.  It’s also an example of why guns will always be available.  Five years ago you needed to be a machinist with tools and quality raw material to make a gun.  Now you need a printer, plastic feed material, a downloadable file and enough electricity to run the device.

I recently read a SciFi story about a father and daughter who had a highly illegal fabricator. A fabricator could make anything if it had the raw materials and the plans.  Dad was just released from jail for fabricating forbidden drugs like aspirin, antibiotics and vaccines for mumps which he sold to the poor who didn’t have access to society’s medical system.

The daughter barely survived his incarceration by making ends meet from the sale of these same illicit drugs while protecting the fabricator.

Dad explains that he learned his lesson in prison and the daughter thinks dad is going straight.  No, dad informs her, he going into fabricating fabricators.  When a need can't be met, people will find a way of supplying it.

Maybe society will come to the realization that a weapon can always be obtained and it’s the user’s actions that are important.  Perhaps vanVogt’s  “The Weapon Shop of Isher” comes to mind.

Ballots Instead of Bullets



Rodney may not have much of a choice, but we do.



Do you vote?
Yeah, I know it’s a mid-term election.  Nobody important running, a governor here and city councilman there and all those judges you know nothing about.  Who cares!

I voted and I’m glad to be done with this election cycle.  I will say your vote does matter.  I helped select the people who will have some influence over our society for the next couple of years, even if it is just the power of the bully pulpit.  And it’s often quite a bit more, too!

In my view, voting and jury duty are two unique privileges.  We had a sales tax increase on the ballot to assist in updating police and emergency communications.  We have the right to say no to that, if we as a group don’t think the police and fire need better communication.  Isn’t that just amazing!  

This blog and others pose the question, "One day will we have to fight in our own backyards, our streets and countryside to keep the freedoms we enjoy now?"   So vote, because thats a freedom we have now! 

By 4:30 I was voter number 200 something.  In my precinct, maybe 300-350 voters will show up by the close of the polls.  I know there are more adults in this area than that.  Where is everybody?  

Listening to NPR I hear reports about attempts to get early voting for the community.  What?  Why worry about early voting?  My poll was open all day and anyone who wanted to vote could.   Only 200 some votes by 4:30.  We get a bigger turn out for high school football.  It’s embarrassing.

Maybe the problem is we make it too easy.

Literature of future societies often portray the right to vote restricted to those individuals who made a major contribution to society.  In one you had to serve faithfully and honorably in the military to vote after discharge.  One society requires complete donation of your personal wealth to society and taking a public service job as the only route to citizenship and that precious vote.

Fiction you say.  Maybe, but it sounds attractive.  Start an effort to teach literacy anywhere to anyone, work for the police, volunteer at a hospital, deliver mail, pickup the trash on the side of a road every three months for a year and then maybe you should get to vote for that year.  You can think of other examples.

That discriminates against…you sputter.  I don’t think so.  You don’t have to have an education to clean up the roads.  You don’t have to be rich to teach children to read.  Turn off the TV for a hour or two each day and do something to engage with society.  Donate $100 thousand out of your millions to the hospital?  Great!  You can get an examination room named after you, but not the vote.  Hold a fundraiser at the corner bar to help the widow of a cabdriver killed in a robbery.  You got your vote.

We take the vote for granted.  We should think of it as a learned privilege.  Think how many politicians would run for office is they had to turn their personal wealth over to society just to be a citizen. 

Sounds better doesn’t it?