Red Dot Sight Physics (How it Works)

[@nomsolo9935]

The led is the focal point of the lens, ensuring the led reflection is normal to the objective.

[@markporthouse]

Very good point. From a technical knowledge point of view, it is worth stating this.

[@garetz2011]

@@markporthouse I am trying to find the equation that defines the shape of the curve and, for me, it seems that the curve is not something with a constant radius. Check out a movie (Marcello MASTROIANNI in "L'uomo dei cinque palloni"); I am going sick trying to find the answer. My CAD says "nope, try again, think more".

[@nrm2022]

Absolutely beautiful explanation, I've been wondering how it worked for a few years now

[@markporthouse]

Before I bought mine, I was clueless as to how it worked! :)

[@soliform3485]

Thanks, this helped me program a holographic sight for a video game!

[@markporthouse]

Pleased to hear it. All the best with the game!

[@lucacollas]

It´s been a year, any Demo of your game? would love to check it out :D

[@africancoalminer1848]

Hey man it's been 2 years any demo or something of the sort coming?

[@xKarmaYT]

Game Developer here, how tf u need this to render a point in the middle of the sight? This is necessary on real life because we cannot attach a red led in the middle of the sight. But on videogames is easy as render it on the middle...

[@barbiefan3874]

@@xKarmaYT it doesn't work that way, if you're talking about "just put a red dot on a piece of glass". The point of holo sight is that the dot ~always stays on the target. We can put red dots on glass in real life too u know. it's called paint.

[@Mr_Rain_Forest]

Wow, this explained all, I wonder what people do on the internet all day, this video is so underrated.

[@xandervanderbroek4637]

Thank you for your well-structured, calm, and easy to follow explanation.

[@markporthouse]

Thanks! :)

[@danli22678]

Thank you, this is by far the best explanation how it works and how to aim a red dot site.

[@markporthouse]

Thank you. I made the video because none of the videos I watched actually explained it, despite claiming to!

[@JackLe1127]

If the LED is at the focal point of the "lens" (we're using the lens more as a mirror in this case), then all you will see is a massive red dot filling up the sight if you look perfectly parallel to its principal axis. The LED has to be put between the glass and its focal point for its image to appear at a specific distance.

[@markporthouse]

Yes, that's a really good point - not something that I'd thought about. If the LED were at the focal point of the 'lens/mirror', the red light would fill up the entire sight (if you were looking at the target, through the sight) and the sight would be useless. So yes, the LED must be 'in front' of the focal point for the light to appear as a dot of light on the distant target (I'm assuming that you are correct, I haven't quite thought this bit through properly yet). Thanks for your comment.

[@tbarnes088]

Optics of mirrors: source is at the focal point of the mirror, so the reflected beam is parallel to the optical axis.

[@markporthouse]

Ah yes, a property of a paraboloid mirror.

[@smeissner328]

Outstanding explanation and clean simple diagrams. Thank you sir, much appreciated!

[@markporthouse]

Ah. Pleased to hear it. Thanks.

[@VoicePlex]

I wish I had opened up the "show more" in your comments above. Anyone else should just skip to about 6:30. Beyond that point the video is very good. Thanks Mark.

[@Ailtir]

The reason the red dot is off so much more at the edges is due to a completely separate effect, related to how looking through a pinhole can let you focus to a further distance.

[@markporthouse]

That sounds interesting.

[@meowmasterL346]

I'm just imagining his neighbors seeing this dude just casually aiming his pistol at their houses 😂😂😂💀

[@markporthouse]

😯

[@1kreature]

Yeah, that was not ideal... Good explanation though.

[@khulegt504]

Thank you, I've been wondering how it worked for a long time

[@markporthouse]

Thanks

[@wm6117]

Your explanation of "REFLECTION" for where the red dot appears is good, but you forgot the "REFRACTION" the target's image experiences as it exits the glass on the eye side. Like a prism the target will appear elsewhere unless a compensating glass on the target side compensates to restore the parallel rays from the target. ie. both sides of the red dot sight lense must be curved. Thank you though, it's a excellent quality video, lot's of great effort!

[@markporthouse]

That's a great point. I haven't discussed how the forward side of the lens has to be shaped (considering the shape of the back side of the lens) to ensure the light from the target continues in it's original direction. Thinking about it, I bet a cheap red dot site doesn't even engineer this in - it may well just have a fixed lens thickness instead. Thanks for your contribution.

[@MegaFrank1960]

@ wm6117............ and that's EXACTLY what separates a $30 red dot from a $300 red dot

[@garetz2011]

In just a few hours all answers can be found on internet. Those chinese from aliexpress are no stupid. To deal with light is just a matter of trigonometry and aplying refraction indexes (1.33 for water, 1.52 for glass, 1.59 for polycarbonate, 1 for vacuum). A good technician can do it. I am studying this for less than a week and I can, almost, see the solution.

[@JoaoPedro-kx6ow]

Finally a real explanation. Thank you so much!

[@markporthouse]

I was as frustrated as you! Videos claiming to explain it and then not doing so!

[@JoaoPedro-kx6ow]

Exactly!!!

[@ruzanna897]

Thanks, very simple and straight to the point.

[@cristianemontagner9616]

Oh... so its a parabolic reflector. Thats probably one of the reasons holographic sights have been getting cheaper, the technology to make parabolic lenses is getting cheaper and easier to do.

[@garetz2011]

I studied something about refraction in the last days and I just gave up! OK, the light goes always to the focus (between center and pole), the red dot it's simple. The light that comes from the target needs to enter a convex face and exits the concave face. I tried with excel with little success. Using the excel numbers in autocad I got a few errors but... a skilled technician won't have problems to define both curves. I'm satisfied, I am not planning to manufacture these things anyway.

[@matthewriegner5180]

I think something I've come to realize is a larger window on a rds can help with issues up to a certain or beyond a certain distance also distance of your eyes from the lense. Example would be using a micro rds on a pistol I can shoot in a straight line up a target from 3-10/12yds but once I get it to 15 is starts to get wonky. Windage is off and even elevation start to shift. And not in the normal shot spread. What's a 1in group at 10-12 yds, becomes a 2-3in at 15. I also have longer arms and if I bring it in a little closer on a bag rest the shots tighten up. It ends up causing issues zeroing at 15 yds or taking longer shots. Essentially because the window is smaller the parabolic lenses curve is more dramatic in a tiny window and slight shifts behind it cause more shift in image. Additionally it's worth understanding what tool for the job. A micro rds is for 10/12 yds maybe 15 depending on shooter and in. I can still be used for further shots but requires more precise lining up in the window.

[@markporthouse]

Interesting thoughts. I'm afraid that I don't have anything intelligent to contribute about the accuracy stuff. However, the lens curvature on a micro RDS should be the same as on a larger RDS, as the micro is just a cropped down lens and must have the same geometry over its area as the geometry of that same area, that same portion, of a larger RDS.

[@zzrzz6199]

People with voices like yours are made to explain things.

[@markporthouse]

That's very generous of you to say. Thank you! :)

[@MJ50]

Perfect video! Just what I needed. Looks like red dot is the way to go especially for self defense... Aim the dot at center mass vs aligning iron sights...

[@wilfdarr]

Really really good description! Well done and thanks.

[@markporthouse]

Thanks. :)

[@calvinhobbs89]

The perfect word for red dot super imposed , when sighted correctly, great insight thank foe your time an great presentation 👍

[@brandonpennington1983]

Now i see what they mean exactly when they say if the dots on it you will hit it. I never had one till yesterday so i had no idea how tjey worked. But with my ruger ready dot, its a 15 moa dot so if its one something it will hit it. With in defensive shooting range of course.

[@TheHexCube]

Excellent explanation. Thank you!

[@andrewmiller6051]

Brilliant explanation

[@markporthouse]

Thanks!

[@scottm2553]

I hope your neighbors don't see you pointing your gun towards their house lol 3:50

[@markporthouse]

:) Yes, it could have freaked them out, even though it was an unloaded air pistol! It's a pretty authentic Walther replica that weighs 1kg (2.2lb).

[@daygeckoarthawaii1360]

Thanks, now I understand

[@markporthouse]

:)

[@Orjan06]

Great video finally I know how it works THANKS 👍

[@markporthouse]

:)

[@quokka_man425]

0:40 “pointing down rAnGe”

[@markporthouse]

:)

[@user-lo4er8wy9l]

very helpful, thanks.

[@01MeuCanal]

How the screw to adjust zero works?????????? How can they keep zero and dont suffer from the shots vibration?

[@ether49]

hey, you said that with your eyes the dot is looking less defined right? that means you have astigmatism. you should get an eye test.

[@markporthouse]

Wow. Impressive. I wouldn't have known there was a connection. I have worn reading glasses for five years now and they correct for astigmatism. I don't wear long distance glasses though. So for using the sight on the air pistol, I ought to get long distance glasses to correct for my astigmatism (even though I'm not short sighted) - ah! Brilliant.

[@RBlatch4d]

Good video. I always try to train my hand to know, but was Curious by the new Protruding gadgetry. 👎 not good enough.

[@laughtonwhitcomb1090]

Very helpful. thanks

[@Dstonephoto]

Is the curve parabolic? Would a hyperbolic , catenary, or circular adversely impact this, and to what extent?

[@markporthouse]

As it is a 3D surface, it is 'paraboloid'. Any other curve simply wouldn't work.

[@talisb7883]

thank you

[@CanisMajor7]

It's 3:29AM. Why i'm watching this? I guess i need answers...

[@samwh.9611]

Great video! Would I be right in saying that the curvature of the lens is parabolic?

[@markporthouse]

I had to look that up. Basically yes, but a parabola is only two dimensional, so actually it is a paraboloid! (Who knew?!) Also, I don't know if it would be described as 'part' paraboloid, because, of course, this reflector (not lens) doesn't even have the tightest part of the curve of a paraboloid - and by definition a parabola or paraboloid is symetrical, which this reflector clearly isn't, as it is only an unsymmetrical part of one.

[@thorick590]

ah yes, so the shape of the lens has to be a 3 dimensional paraboloid so that all light coming to its curved surface is sent to the location of the LED, 'the focus of the parabola' and vice versa, the light emitted by the LED is always reflected straight back. All that time studying Analytic Geometry wasn't a waste of time :-).

[@sayochikun3288]

Im glad neighbour didnt call the police at 4:30

[@DiveTheseClips]

Thank you, this is a great explanation! I finally understand how this thing works.

[@joeabad5908]

Click Bait. Title reads Red Dot..Video show a GREEN Dot.. Lol.. Nice presentation though.. Thanks for up loading..

[@markporthouse]

LOL! Brilliant. You had me going for a moment there! :)

[@xtrchessreal]

Good stuff, I was thinking of buying one of these for my Glock. Simple enough. Keep your eye in the center of the lense and the dot on the target you should hit the target+/- any pull or push from your trigger break force and the quality of your support hand. On the other hand I might not need one of these on a handgun at all if I'm shooting 3, 5, 6, 8 yards away from a would be assailant. 25 yards I see some people going for. How can you tell if they're intending to do you harm at 25 yards? I suppose in combat things are rather tricky, moving targets etc. I only plan on keeping myself from being overtaken at short distances. If rifles are involved its a completely different tool needed and a handgun is nearly worthless. Anyway thanks for the great tutorial.

[@markporthouse]

That's an interesting view. It's so different to here in the UK where very few people would even be thinking about encountering anyone threatening them with a gun. But thanks for your comment - I'm sure many will find it insightful (as indeed it is).

[@xtrchessreal]

@@markporthouse Yes the USA has lost its mind well before Trump but he made things much worse. Everyone when I grew up was civilized and people that had any guns at all, were hunters, many police officers weren't required to carry them. Now, all police departments are fully required and have a full compliment of war machines in the name of self defense from criminals. And then you have the public now seeing these police wearing military grade defense materials, politics that divide us from each other and a 2nd amendment that states every citizen has the right to bear arms. Many of which have been purchasing for several decades but highest % sales of guns since Trump was elected and an even larger spike up since the attempted coup on Jan 6th 2020. That day many consider to be a well planned concerted effort to topple our current Republic with representative Democracy to an Autocracy or worse. So now we have extremism on the right and the left gearing up for a civil war that may never happen but just in case it does. The gun manufacturers love it, ammunition MFRs can't keep up with the demand. Then we have Putin losing his mind along with China poking the fire. I just want to be able to survive an idiot trying to break into my house during a riot or something of that nature. In this country you have to believe everyone has a gun at this point, calling up the police to protect you from a break-in or whatever, you may as well be putting your head on a chop block and asking for an executioner to swing his axe. I mean the wait time for help is too long. Natural disasters tend to bring out looters etc. I can't prepare for every scenario but being a little prepared can't hurt. If I could I wouldn't be living here at all. I'd rather be somewhere more relaxed and just living a nice stress free routine.

[@inuyasha9311]

Thanks

[@RwP223]

This guy is an American, if not, in Spirit.

[@markporthouse]

:)

[@jmigsan]

Thanks!

[@goodebatcher1960]

It must’ve been so weird for his neighbours to look at one of his windows and just notice a guy with a gun pointing it at their house

[@markporthouse]

Yes, they might not have realised that it was a .177 air pistol!

[@wamm2891]

Does the bullet hit the same spot the red dot is sighted

[@markporthouse]

Well, in my case a pellet, with it being an air pistol, there are the usual inaccuracies, but not due to the sight being wrong. The sight is fully accurate when the dot is in the centre and it has been set correctly. The accuracy would be compromised slightly when the red dot is not in the middle of the sight, i.e. when you aren't looking from directly behind the sight. Although the point of the optics is to keep accuracy even if your eye isn't directly behind the sight.

[@kenrobba5831]

Bravo !

[@markporthouse]

Thanks. :)

[@liujordan3505]

Saw your video and found it very helpful. I happen to have some sights, tripods and other objects here, and I am looking for someone to help test the product. If you are interested, you can chat.

[@maxzzzie]

The neighbour is on the phone with the cops currently.

[@markporthouse]

:)

[@wilfdarr]

Was thinking the same. That said, it's Britain, so no one has a real pistol (not even the Olympic team: they have to train in Ireland 🤣😂🤣😂).

[@greengoggles]

Gun is static, camera is moving

[@markporthouse]

Yes.

[@a_asp829]

Thank you❤❤ i just made one out of cardboard lmao🤣

[@royclark2269]

Incorrect sight picture; violates basic US firearms safety practices.

[@markporthouse]

I think that people would be interested in more information about your comment.

[@marsoelflaco5722]

🤷🏽‍♀️