Can we see single photons?

Light is made of photons, and our night vision is limited by the ability of our visual system to detect these photons. In some ways, our eyes approach the fundamental physical limit for light detection, being able to detect light flashes of less than a dozen photons.
This video is copyright (c) 2021 by Kerry Kim. No part of this video may be used without my prior written permission, except as permitted by U.S. copyright law.
Animations were made in Maya and Blender by Kerry Kim.
0:00 Introduction
0:37 Photoreceptors and photons
1:52 Experiment
3:22 Rhodopsin
3:59 Signal to noise
6:00 Limitations
6:55 Conclusion
References:
Hecht S, Shlaer S, Pirenne MH. Energy, Quanta and Vision. J Gen Physiol. 1942 Jul 20; 25(6):819-840.
Baylor DA, Lamb TD, Yau KW. The membrane current of single rod outer segments. J Physiol. 1979 Mar;288:589-611.
Rieke F, Baylor DA. Single-photon detection by rod cells of the retina. Rev Mod Phys. 1998 Jul 70(3):1027-1036.

[@KerryKim]

To see how light leads to producing an electric signal, see my next video here: kzbin.info/www/bejne/hJvVd5htf62MZ9E

[@Reth_Hard]

OK but what size is this snowflake exactly? Is this one of those that are so small that you can only see them around bright spots of light or maybe is it the size of a golf ball? And what about the weather, is there any wind? What if it falls during a blizzard?

[@specific_pseudonym]

@@Reth_Hard a quick bit of googling found a mass of ~3mg on average. A bit more gives a speed of 0.67 m/s. Assuming that the ground impact absorbs all the kinetic energy of the snowflake, that means the impact imparts energy 0.5mv^2 = 0.5(0.003)(0.67^2) = 0.00067 J. Now, sure, a faster snowflake will have more kinetic energy, but my bet is that the calculation used was this very simple one.

[@specific_pseudonym]

@@Reth_Hard so, that snowflake has 0.00067/(4.04×10^-8) = 16,590 times the energy of the light pulse sent to everyone.

[@specific_pseudonym]

Oh okay thanks KZbin, for deleting the post calculating the energy of all the photons -_- (it is 12×7.67×10^9×hc/λ where lambda for blue light is 450nm. Or 4.04×10^-8 J)

[@brettmoore3194]

Why believe in photons,electrons, and other particles if science can't validate through empirical evidence. Dr. Paul.m.brown proved that thorium emits a wavelength not a alpha particle. He also proved that a higher amplitude inverse frequency of a radioactive source will make it no longer radioactive... Any thoughts

[@Ranstone]

I discovered the superior peripheral night-vision thing by myself, and always thought I might have damaged my high detail rental area from staring at screens... Good to know it's normal.

[@Iam-nw9fw]

The optometrist should have let you know that, after they let you know you're ugly, since one eye is higher than the other.

[@EVRLYNMedia]

same, I found it so strange...

[@downey2294]

@@Iam-nw9fw i don't get it

[@anapaola7241]

Why where u staring at the corners? Trying peppermints Buttler trick?

[@sen7826]

*retinal lmfao

[@GarryDumblowski]

It honestly surprises me that our eyes are so good considering how much tinier the things that are being detected are. Your nose detects entire molecules, your ears detect broad patterns in fluid current, but our eyes detect _fundamental particles straight out of the standard model._

[@jamescheddar4896]

and you "minds eye" can detect things that don't even exist yet

[@combomaster99]

This just shows we're biological machines operating on molecular level. I feel like we don't appreciate this enough.

[@solaokusanya955]

Deep ...I just got an epiphany at this realization

[@MikkoRantalainen]

To be exact, the eyes are not directly detecting to photons but the molecular changes that the fotons cause in the cells when the photon hits the molecules in the cell. Still the sensitivity is surprisingly good considering that the light sensing surface is backwards in the skulls of all mammals. We could create much better eye by taking the sensor surface from an octopus which doesn't have similar backwards implementation, light reflecting surface from a cat and lens material from an eagle. This alone should be good enough hint to religious people that eye was not designed but its a result of evolution.

[@duncan.o-vic]

A photon is the smallest detectable amount of energy by definition, it does not really exist untill light waves interact with molecules in your eyes.

[@FelixHelix]

I have always experienced a phenomenon called "optical snow" or "visual snow", where there is a dull white static flashing over everything, constantly. It's faint, but especially noticeable if my eyes are closed, or the room is dark. It's similar to the effect one gets by rubbing your eyes until you see flashing lights, but constant and not as prominent. However, it is very annoying, and at times it is worse than others. It seems to pair with my tinnitus. I fully thought that it was normal and everybody experienced it until I was 16, when my optometrist had no idea what I was describing when I told him about the "faint bright white flashing everybody has".

[@Versuffe]

same.

[@evil1knight]

Yeah visual snow isn’t great :( gets worse with stress, got tinnitus too, just static on all senses. My theory is we have a broken noise reduction in our brain, I think all people have visual snow and some tinnitus but the normal brain can filter out that noise like a digital camera or noise reduction on a microphone, ours just doesn’t work properly anymore

[@matthewfontaine4928]

A faint bright light.

[@FelixHelix]

@@evil1knight Tinnitus comes from little hairs falling out of your ears. It's like using the radio with a snapped antenna - static, white noise. Optical snow stems from nerve damage.

[@olegshevchenko5869]

I've been able to see tiny colorful dots faintly flashing around since as long as I can remember. I was 25, I think, when I first learned that wasn't what everyone else saw. It isn't as bad for me, though, in most cases I find myself being able to make out small details better than most everyone, so it can't be that bad. I have tinnitus too, though, and that one is a bummer, but thankflly I've got used to it int he past few years since I first got it.

[@hipphipphurra77]

Congratulations to his high quality contribution. This deserves a million views.

[@teslainvestah5003]

Amen!

[@tolyko9159]

If it's in my recommendation feed it will be there quite soon

[@stampy3335]

No it doesnt

[@stampy3335]

It needs 1 trillion views.

[@terrsus7676]

Quarter way there.

[@reinux]

That's pretty cool how the rods are off to the side a bit. Day time = hunter mode, need to see ahead Night time = prey mode, need to see to the sides

[@YesPlease964]

That...actually makes alot of sense. Can someone confirm?

[@NGC1433]

@@YesPlease964 I think it is the reverse of that logic - center, hunter mode has no space for slow and colorless rods. Most of our "resolution" is in the very center of our field of vision.

[@chrisflanagan7564]

many hunting animals aren't very concerned with colour, cats and dogs both have worse colour vision that us. Our strong colour vision is very good at identifying ripe fruit. Fruit eating birds have even better colour vision. We're omnivores, our high detail colour vision is as likely to be advantageous for picking ripe fruit as it is for anything else. Yes, our high detail binocular vision is good for picking a distant target out and throwing something at it, or chasing it, but I think the colour vision is more plant oriented. Cats are pure hunters, and they don't have any where near the detail vision that we have, let alone colour. But they are famously low light hunters. Hawks have good colour vision, and they're day hunters, but they're cheating by being birds ;) Many predators seem to have more limited dichromatic colour vision, and I've seen a few articles that say simpler colour vision seems to help them cut down on visual noise and find camouflaged prey faster. blah blah blah, it's a rich tapestry. We have a great mix of night vision and colour detail vision.

[@reinux]

@@chrisflanagan7564 never knew that about color perception

[@marikasdaughter6263]

@@YesPlease964 Confirm what? It's a thought nothing more... It's not true though, it's a happenstance of how our eyes are designed but there's no higher being designing us being like "OHHH this will be good so they can defend themselves at night better yes, must make it like this..." This is just how our eyes are, the sides have less importance for colour since the vision clarity is poor so the space is filled mostly with rods which in turn gives a better night vision because more surface area dedicated to collecting light instead of colour.

[@denispol79]

As a visual astronomer, that was very compelling for me. I read a similar russian paper that was published in the soviet era. So, comparing the human eye to modern astronomy cameras, with their quantum efficiency of ~70%, the cameras have surpassed it. Also, once rhodopsin detects a photon and starts a chemo-electric reaction that leads to neuro-signal, it has to deactivate, and it takes time. Also, unlike the cameras, there's almost instant exposure time. While the camera can collect light during long exposures.

[@Astrofrank]

Most current CMOS cameras have at least 80%, many CMOS cameras have more than 90%, CCD cameras can reach 99% QE.

[@kummer45]

This man deserves better. Outstanding video. Many people like him deserves better in the industry. His high quality, humble approach and coherent exposition granted him that opportunity.

[@jamest.5001]

I woke one night a couple years ago, because it was so hot, it was hot because the power was out, in the whole small town I live in. I went out side, it just happened to be a very clear sky, and no moon, I could see stuff I never saw at night, and the stars, the sky, it was amazing!! It was like a spiritual experience, I couldn't stop looking at the sky, I could see 10x more stars than usual, and alot had a. Red orange color to them, it was crazy, nothing was normal! It makes me want to move to the middle of nowhere, and just look at the sky, my eyes were adjusted as much as possible to low light vision, because I had been sleeping for hours, and no lights to foul my night vision, the only light was the natural star light, and the light pollution from towns probably 20miles away, the night sky is far from darkness, we dot realize that so much anymore, I'd love to see that again, especially with binoculars... It's amazing how much light there is in the night sky! Great video!!

[@spacemanclips]

I had similar experiences when young. Treasure them, because you don't / can't see them as you get older!

[@arseniix]

Haha, finally you've gotten appreciated by the algorithm, congratulations! Remarkably great video.

[@skyman1693]

The fact with the radio telescope blew my mind! I never thought about it, but it is unbelieveble how less energy a low frequency photon carries.

[@therugburnz]

I learned in Astronomy that I and most others can see better from the sides of our visual field. Yes, 20° of angle sounds correct. I'm partially color blind and notice it well. I was doing a visual observation of a nearby galaxy. I could not see it at all until I concentrated my attention to the sides of my visual field. It made it difficult to draw until I was instructed how to "see" from the 20° position.

[@victorcercasin]

I love when people explain things in an objective, deep manner interest of making dumb analogies Ana simplifications Great explanation

[@NondescriptMammal]

Absolutely agree! Even the best analogies really do not serve as explanations, they just dumb down the explanation in a condescending way, like "you're not smart enough to understand the actual explanation, so here's an analogy instead".

[@tothejazz4828]

Yeah it's just a weird artificial layer for children or something. Like "imagine a photon is like a car, and a rod is a garage" or something

[@leejerrett8268]

@@NondescriptMammalA term I love for this is ‘Lies-to-children’ from ‘The Science of Discworld’:”A lie-to-children is a statement that is false, but which nevertheless leads the child's mind towards a more accurate explanation, one that the child will only be able to appreciate if it has been primed with the lie”.

[@NondescriptMammal]

@@leejerrett8268 Frankly, that sounds like an awful way to teach anything, even to children.

[@HallyVee]

Some odd biases against analogies here. They're just handy linguistic tools, the context determines their intent. Also remember some are used to simplify so as to save time and spare another disinteresting content. A tool that builds a weapon is still just a tool ;)

[@oceannuclear]

Thanks for providing the actual timescales and the graphics! It's very useful for figuring out what's the true timescale over which things happen. I'm also surprised (but probably shouldn't be) that noise suppression is a problem that plagues cameras and biological creatures alike!

[@alitazabekov3819]

Wow, what a nice explanatory video! I see so much work put into these animations - and they support and complement the narrative really well! Thank you so much for this video! I wish there were more of such quality videos!

[@krzysztofjakubiak673]

A very eye-opening video. The explanation and delivery are both excellent!

[@Roberto-REME]

Excellent video production Kerry, and you did a great job presenting the information in an interesting and engaging manner. Your narration is superb. Well done!

[@tjeepert9782]

I have just discovered this video and I already love it. This is some serious quality stuff

[@gizfpv]

Very good video. Nicely presented. Fun fact (that you may or may not know), night vision headsets that are used by the military always show images in green because (as you mentioned in your video) rod cells can see greenish light better than any other colour :)

[@JohnDlugosz]

Likewise, a turquoise LED (monochromatic) makes for a keychain flashlight with the greatest ability to illuminate the space around you for the least amount of battery power.

[@a2e5]

and red is used for illumination during stargazing (& ship stuff) because they are least likely to mess with dark adaptation by overwhelming and bleaching rod cells

[@labibbidabibbadum]

I'm glad I found this channel. Delivery and content are perfect.

[@xkinsey3831]

Ever since I was a kid I always wondered why we see a kind of noise or static-like effect in the darkness, this just answered one of my life-long mysteries!

[@carnsoaks1]

That was freaking enjoyable. You and your team should be proud of the unreal graphical presentation, that field of rods, the close ups of rods and cones, the information that graphic revealed. Deserves a Ubbie Science Communications Award.

[@lumi2030]

this is surprisingly high quality, especially the scripting and narration. the answer to the titular question is also satisfactory

[@Dartagnan2717]

Very well done and easy to understand. I look forward to your future videos.

[@j.m.dirassar]

could that "background noise" of small tiny flashes in the dark have something to do with any kind of cosmic particle or wave? sorry for my ignorance on the subject, I've really loved the video for its plain language, thanks a lot

[@carlgeorgbiermann2915]

I think that normal noise is due to the thermal motion of particles. It is a general principle that more sensitive detectors need to be cooled further down in order to reduce false triggers of the detector. HOWEVER, I recall hearing that astronauts reported seeing flashes in the dark (which should be more intense than the ones we perceive at the surface of earth). These are caused by cosmic radiation hitting their retina.

[@martinsimeonov1563]

Well, to answer this question, you could see those indeed. As light flashes. BUT: they are quite rare. Most times it is ftom something else entirely so you wouldnt know if it was due to a cosmic particle or not

[@VJETRA]

just massage your eyes and you'll see those magic cosmic optical every where lol

[@MrSebastian2203]

@@VJETRA but that’s your blood and white cells interacting, your brain can filter out those imperfections (veins and other stuff in eye) but putting an object in front of your eye and quickly moving it back and forth causes you to see those things. It’s because your brain can’t keep up with change of the shadows that your veins throw and does not compensate yet. There was a video about this somewhere. Also pressing on your eyeball triggers the nerves too, you are not seeing energy particles, just your stuff in eye.

[@luisgalleguillos4868]

@@carlgeorgbiermann2915 what is the difference between cósmic radiation or particles and photons. I live at 12tjhousand feet and see no cosmic particles at night.

[@mikeoliver3254]

Fascinating, thank you for the education about rods. Looking forward to more videos.

[@anhi399]

Loved this--not just educational but wondrous as well. Thank you for sharing your video!!

[@Bungifun]

wow, great presentation! Short enough yet detailed enough to have a more advanced understanding

[@HasBeensNAddicts]

So happy I just found your channel. Time to binge watch. edit: Easy binge watch since there's 2 videos lol. Can't wait for more

[@DEtchells]

Very nicely done piece! I’ve subscribed, will watch for more!

[@BS-vx8dg]

Fascinating. I've never come across your channel before, and I'm glad this popped up on my feed.

[@blackmagicprod7039]

Don't know what to say. This video blew me away. I really love the references in the description. Including DOIs should be mandatory, and I appreciate you for it. Thanks for what you're doing. Subscription earned.

[@beatbox20fmj]

Not what I was looking for but still very well put together video. Enjoyed it, thanks!

[@ibaba9270]

High quality.Deserve more views.

[@AwwhHex]

Your channel just came up on my feed out of no where and I’m so glad it did. This was super informative and easy to digest, especially with the diagrams. :)

[@luc4662]

I had never asked myself that question, but when I saw the title, I thought: « wow, good question! I don’t know! ». Great video.

[@ryanatkinson2978]

Very cool video, this is a question I've wanted answered for a long time but couldn't get a straight answer to. I was curious to see if I could detect the glow from thermo luminescent dosimeter crystals. Your channel needs more attention!

[@natedewaele1861]

I liked this. Would like to see more from you. Physiological processes are cool, eyes are cool

[@mdellertson]

Thank you for producing such valuable information. I can only imagine how much work creating all those shots and graphics must have taken. Not to mention the years of study to learn all the knowledge you shared in this video. I can’t wait to watch more of the videos on your channel!

[@hamdanmahmood346]

Holy hell, dude this is awesome; kept me hooked from start to end!

[@brunorivest]

Very clear explanation. Informative. Very interesting angle and topic. Thanks a lot for that video. I'm not a physicist, but I'm glad those who know some about it can bring the topic to the masses.

[@ScottHaigMD]

Great, great explanation. We think the Sagan claim is off by a few orders of magnitude but the general idea is appreciated. Thanks for your work.

[@thoocas]

This is such a logical, concise, and well thought out presentation. A joy to watch. Thank you!

[@Roberto-REME]

Outstanding video, Kim. You explained really well the concept using superb graphics and your narration is outstanding: engaging, interesting and informative.

[@red-baitingswine8816]

Great topic and great explanation - clear/simple/accurate/complete.

[@english_chat]

I have single small luminescent star attached to the wall in my room. At night I noticed that I only can see it with my periferal vision, and couldn't see it when I look straight at it. I thought it was because of the bacteria dots on the middle of my eye. But now I understand the real reason why that happened, and my eyes might be totally alright. Thank you! 👏👏

[@keithrelyea7997]

Wow, what a wonderful lession. Clear explanation and great visuals. I've added you to my suscribed list.

[@dzfz2100]

Just discovered this channel - incredible education content is such a precise and direct format. Subscribed! Hope there is more some day!!

[@jonahansen]

Excellent presentation well narrated.

[@mysock351C]

The noise is definitely noticeable. In near total darkness I notice that I could actually see if the noise was not there. It makes it quite difficult to resolve things. Of course one would think you could just have a reflective layer behind the retina like animals, but that's likely to result in a substantial loss in resolution at the center of the eye to the fact that there will inevitably be some diffraction of the light. In our retinas the light is pretty much totally absorbed by the melanin, so there wont be any secondary detections which is what you want for good resolution. In that regard, the eye does strike a nice balance by having very good detail but still having reasonable SNR under most conditions. As with anything involving signals, there are always trade-offs to be made against sensitivity, noise, and response.

[@jamesstewart7212]

So is "noise" an actual photon event? I don't think we can ever know.

[@MrPinknumber]

This was so well expained, I managed to follow everything. Awesome work :)

[@andreeaalecu4996]

Hi, Kerry have courage, looks like inception of a beautiful science channel!

[@PotatoflakeJake]

This is incredible thank you

[@Komatic5]

Really interesting video. I thought it was weird that I could see better in my peripheral vision at night but this is reassuring.

[@RP-mm9ie]

Remarkably great video. Keep it up, great voice ,great visuals, will become a popular channel. Subbed.

[@michaeldebidart]

I was about to ask if the "noise" in the receptors was why in darkness I could swear I see a faint static in my vision but as I was typing it you explained that very phenomenon. You got my sub.

[@kunalhalder615]

Brilliant question, brilliant explanation

[@gregorymccoy6797]

Very well done. I loved it.

[@CharlesLeak]

Terrific video. I knew that the first scintillation counters were grad students locked in a dark room staring at ZnS screens... but I'd never considered their quantum efficiency. I hope you make more videos!

[@AlexandrKovalenko]

Extremely interesting video, it is a shame it has so small number of views...

[@kinshuksinghania4289]

Factually wonderful!!

[@Everett-xe3eg]

100 years! Wow, great video! Thank you

[@mats1975]

I've always wondered where this "white noise" came from or how it was produced in complete darkness , thank you for explaining that! Makes a lot of sense, similar in a way to the white noise of a TV or a radio in absence of a signal.

[@qlifee]

I have a question that will be a good video topic: 1- What are the limits of the eye to seeing at low white contrast. 2- Limit to seeing smallest angular resolution. 3- Limit to seeing both lowest contrast and smallest angular resolution.

[@okboing]

this explains a lot, why i thought staring at screens damaged my foveal rods' sensitivities, and why i can't see color i the dark! i thought these were problems, turnns out they're super common!

[@matthew2091]

I am amazed that even though all photoreceptors are not strictly aligned, our brain can still arrange all received signals into pictures. Thanks for the great demonstration.

[@Votrae]

What a cool revelation about single photon vs. single photon to several rods!

[@Vinkabbeats]

thats what the fuzz is when your looking around, its so fine yet definitely noticeable , all the photons being processed in "real" time

[@EdwardCurrent]

Fantastic job! I do videos like this and this one is perfectly done.

[@msimonsen3344]

Very cool video. I hope you do more.

[@ImageJPEG]

My mind has been blown. Thanks for explaining why I can see dim stars at night when I’m not looking directly at them but disappear when I look directly at it.

[@user-wz7ch8vf2p]

man, that's great

[@Troglodude05]

Question. You know “Visual snow?” I haven’t been able to find a very clear answer on at least the specific affect of seeing faint TV static all the time. Is that caused by rods randomly firing? Or something else entirely?

[@cobaltnightmare5920]

There isn't a very clear answer yet but it could equally have as much to do with our brains as it does with our eyes. Apparently, it's more common in people who have used LSD and also in people with ADHD.

[@aphexau]

Your video deserves more views and subscribers. It is excellent. Please make more

[@Ogaitnas900]

Great video! Really, all the visual aids were great, the script and recording too.

[@linyenchin6773]

This matches my own experience. Thank you!

[@krzysztofjakubiak673]

xD I can confirm I too experience this.

[@professordanfurmanek3732]

Retired University Astrophysics Professor: A truly brilliant explanation of how the human eye works! No college level Astronomy class should ever begin without viewing this! Kudos on a magnificent blend of both biology and physics!!

[@dancoulson6579]

I was going to ask what color of light the rods are most sensetive to. But you included it in the video without me even needing to ask. Thank you.

[@c.s.842]

Thanks for such an instructive video. Please keep posting.

[@hiddenshadow4550]

I can confirm, my rod is very sensitive

[@jezusbloodie]

The static noise you can see in the total absence of light has a name, or at least it's colour has; Eigengrau. German for some something like "intrinsic grey". Also known as "Eigenlicht" (Dutch/German for "intrinsic light") The RGB value is 22, 22, 29.

[@vkgamingplatform7247]

I was always thinking over all the topics discussed here.grt work

[@exxodas]

Your narration potential is unseen!

[@csquaredfilms]

4:25 im gonna make a bold guess and assume this is why when im in a really dark room my eyes do this really hard to describe thing where basically everything has this kind of static over it? by the way, this video is awesome. the amount of effort put into it really shows. i wish there was something i could do to spread it but sadly not many people are interested in this stuff so all i can really do is leave this comment :p edit: WOW i shouldve watched a little further than i did, not even 30 seconds later and my question was answered

[@Major00Tom]

Didn't know this flavour of nerdism was available. We live in wonderful times (in some departments).

[@colinadevivero]

Excellent writing and delivery

[@johncaporaletti6103]

This was outstanding. Great work

[@sobreaver]

Biology 'understands' probability ?! o0 Great narration, interesting content !! The smallest details we are meant to detect yet the 'biggest' mysteries remaining unknown ;)

[@AlexeyFilippenkoPlummet]

In all your travels, have you ever seen a star supernova? No? Well, I have. I saw a star explode and send out the building blocks of the universe. Other stars, other planets and eventually, other life. A Super Nova, creation itself. I was there, I wanted to see it and be part of the moment. And you know how I perceived one of the most glorious events in Universe? With these ridiculous gelatinous orbs in my skull! With eyes designed to perceive only a tiny fraction of the EM-spectrum! With ears designed only to hear vibrations in the air! I don't want to be human! I want to see gamma rays, I want to hear x-rays, and I want to smell dark matter! Do you see the absurdity of what I am? I can't even express these things properly, because I have to conceptualize complex ideas in this stupid limited spoken language! But I know I want to reach out with something other than these prehensile paws! And feel a solar wind of a supernova flowing over me. I'm a machine, and I can know much more, I could experience so much more, but I'm trapped in this absurd body! And why? Because my 5 creators thought that God wanted it that way.

[@fer86bd]

applause for you!! this is an EXCELLENT explanation

[@W00PIE]

I haven't thought about vision for a long time now, you take things for granted after a while. I am awed by the fact that time and evolution has led to such an incredibly useful instrument (and yes, the human version is nothing compared to some other species). And it makes me acknowledge even more the fact that some of our kind have lost or were born without the ability to see and nevertheless adapt to that fact and compensate the lack of vision with an unimaginable improvement of other senses. Nature is fascinating, spooky, scary and comforting. Thanks for the video!

[@deaddoomed2380]

this channel deserves much more attention

[@sa2-2k14]

AMAZING video and explanation. You're incredibly talented and compelling to listen to

[@ryanburbridge]

Over a year? Such a great video. Please make more.

[@pauld8747]

I really liked the way you explained everything, and the order in which you did it. It was very easy to follow and you answered every question in my mind

[@itscky2007]

Very great visualisation and explanation,totally underrated

[@petri1698]

This is the best video i have ever seen! amazing work!

[@LucianoJuly]

Much enjoyed. Great presentation of graphics.

[@davidblyth5495]

Excellent presentation. It also explains the procedures we used in the military when operating in dark environments

[@goldenredstone04]

Such an interesting video from start to finish!