The Fresnel Lens: the Invention That Saved 1000 Ships

Like what I make? Want fewer sponsorship ad reads? Consider contributing to my Patreon at / ourowndevices
Perfected in the 1820s, the Fresnel Lens is a lightweight, low-profile lens composed of annular segments, originally developed for use in lighthouses. The design allows for the construction of extremely large lenses that can collect and collimate nearly all the light emitted by a lamp and project it over large distances. As well as lighthouses, Fresnel lenses are used in a number of other applications, from theatre lighting to lightweight home magnifiers.
SOURCES:
uslhs.org/hyper-radial-lenses
www.smithsonianmag.com/scienc...
www.michiganlights.com/fresnel...
www.lighthousefriends.com/lig...
uslhs.org/lens-use-prior-fresnel
uslhs.org/fresnel-lens
web.archive.org/web/200709270...
www.bbc.com/travel/article/20...

[@ProfPoindexter1968]

Fresnel lenses are also used in cataract surgery, where a tiny hole is laser drilled in the cornea, the clouded lens is shattered by an ultrasonic probe and vacuumed up by a tiny tube, and then a rolled up, plastic fresnel lens is inserted into the eye to replace the natural lens. When released, the plastic unrolls and installs itself in the eye. The whole process takes about as much time as it took for you to read my description. I have one in each eye, and can see 20:20 now, though oncoming car headlights at night produce slightly more glare than they used to. I LOVE my fresnel lenses!

[@gelo1238]

Very interesting. Thanks for sharing that story!

[@mandolinic]

I've been told I have a small cataract which might require treatment in future. It's reassuring to know that you're happy with your new lenses.

[@maciejtomkiewicz6733]

I have a pair implanted too.

[@senatorjosephmccarthy2720]

I don't know how you can even drive, seeing the numbers 20 20 in your field of view.

[@kaitlyn__L]

That's interesting, my dad had cataract surgery recently and mentioned the artificial lenses - don't think he specified they're fresnels! How's the fine detail when not from a light source? Any distortions or chromatic aberration on eg small text like those magnifiers he brought out?

[@tracylemme1375]

On the island of Great Inauga in the Bahamas is a lighthouse that was built in the late 19th century. It has fresnel lenses about 1 meter in dia. It still burns kerosene and uses a mantle about 100 mm in dia. The lens house is rotated by a massive escapement mechanism. The keeper must winch large weights from the base to the top of the structure,and pressurize the fuel about once an hour. Very impressive.

[@gelo1238]

I was curious how lenses were rotated, and i though about escapement mechanism like in clock but i denied it because it would need to be wind up pretty often. Seems like i was right and wrong lol

[@nathansmith1085]

Is this the one that Alex E Karnes ran? I recently found him on The Proper People and I'm extremely interested in him, I love his passion and knowledge.

[@tracylemme1375]

@@nathansmith1085 I can’t remember his name. Maybe I never knew it. But his knowledge of the entire system impressed me. At my age I find that many people such as him are no longer with us. He did teach me a lot about his particular lighthouse and the whole lighthouse system.

[@dustypulver1]

Yet another invention that was NOT created by American but is claimed by a yank to have been.

[@shinola228]

Someone should make a video of the inner workings of that lighthouse.

[@frenchcreekvalley]

Let's not forget the "overhead projector". for transparencies. They were used in schools and meeting rooms all over the world from about 1962 until just a few years ago.

[@fricki1997]

Here in Germany I wouldn't be surprised if many schools still use them :D

[@alycatpublishing1164]

@@fricki1997 Don't feel bad. There are some places here, in California, where they still read by candle light although this has more to do with politics than technology. :D (That smiling face doesn't work here.)

[@Matthews_Resume]

@@fricki1997 If it is not broke do not fix it :D

[@Shinzon23]

Oh they are still used everywhere. It's a old tech, but kept as a backup in case the computers go down

[@gupwalla961]

Back in the mid-80s, my school held a statewide “Computers in Education” conference. Apple was on hand to show their new computerized projection system - which was a flat glass monitor that sat on the traditional overhead projection machine. I don’t think I ever saw one used outside of a tech demo, but 11-year old me was suitably astonished.

[@TexDrinkwater]

I'm a bit surprised that you didn't mention the once ubiquitous overhead projector that used to be found in every classroom and conference room.

[@jonnyphenomenon]

I've got a handful of those fresnel sheets from old transparency projectors. They work great for starting the camp fire.

[@ArkhamHedler]

And Projection TVs.

[@cbroz7492]

...it's nice being old..we remember such stuff..

[@TexDrinkwater]

@@cbroz7492 ... I remember stuff...for now. 🤷‍♂

[@MajinOthinus]

@@cbroz7492Come to Germany then, where they are still in undiminished active use. You'll feel like you're in your childhood again.

[@Ariolander]

Fresnel Lenses are famously used in Virtual Reality headsets! They are used to adjust your field of view in the headset and make the screens seem to wrap around your face improving the immersiveness of the technology.

[@Spritetm]

Also, less recent, overhead projectors had one that focused the lamps beam to go through the top optics.

[@TedwardsTube]

I came to add this comment as well, but see someone beat me to it. I’ve of course seen and used variations of fresnel lenses a number of times, but never knew what they were called until recent years when Virtual Reality has become a big hobby / area of personal interest for me, and so I’ve continually heard them talked about. They’ve been the most common type of lenses used in VR headsets, as I understand it, because they’re relatively low cost. But in 2023-2024 the better headsets are finally moving on to better quality lenses that don’t cause so much image distortion, god rays, and generally unpleasant light refractions.

[@Shinzon23]

There are also why you're told not to leave the headset where some light can fall on it because the lens will focus the sunlight and burn the internal screens

[@ChristopherSchreib-yn1vu]

What if we set up a very long copper pipe, with exposed intervals between mostly thermally insulated pipe sections, and set up mechanisms along it, that focus sunlight onto the copper pipe using modern, thin plastic Fresnel lenses, so that by pumping air or inert gas into one end of the pipe, it will jet out the other end like a BLOWTORCH, to use the FREE solar heat for industrial purposes?

[@WarpRulez]

No, fresnel lenses don't somehow magically make the screen look like it "wraps around your face". The reason why they use fresnel lenses is because they achieve the same amount of refraction with a much thinner (and thus lighter) lens. A regular lens would technically be better for VR, but it would be really thick and heavy, causing the headsets to be bulkier and heavier.

[@robertgoss4842]

This video is among the very best I've seen on YT. No muss, no fuss, just pure subject matter info. To its author, I say well done, indeed.

[@ernestyeagley512]

I addition to maritime use, the Fresnel lens has been extensively used (and still is) used on US railroads on many signalling applications for almost 150 years. The application of the Fresnel lens was especially important during the use of kerosene flame to illuminate a signal device lens, and low intensity electric bulbs annulling the use of kerosene flame later on. The Fresnel lens greatly magnified the dim flame and if not quadrupled the light output of the flame increasing its visibility to project the aspect color (either red, green, yellow, blue or purple, and even white) of the signal whether it be marker lamps on the trains themselves, track switch signal lamps, and was even used on early railroad crossing lamps that were attached to the gates at a railroad crossing. Just about every application requiring to project the purpose of a "signal" used a Fresnel lens. Since various colors of the aspect was used, the flame or light behind the lens had to be greatly magnified, especially for the blue and purple lenses. Even with the bright 12v bulbs in way side signals (now gradually being replaced with LED) the Fresnel lens is used to even further brighten an already bright kelvin output of the signal light source.

[@bebera487]

You also probably carry one of these with you most of the time since every smartphone flash has a tiny little Fresnel lens inside it to help it focus light. Fascinating stuff really.

[@rfinkels22]

Since I am a theatrical lighting designer I can say with 100% certainty that the lens on the desk, while indeed used in theatre, is NOT from the lighting unit he claims, the Fresnel Spotlight, but rather used in an older version of the type of theatrical spotlight called an Ellipsoidal reflector spotlight. The Fresnel Spotlight he showed does use a Fresnel Lens but of a totally different design. If you look at the spotlight in his film clip you can see the difference, The lens on his desk is of optical quality which the ERS spotlight requires as the ERS is in essence a projector without a fan. Any metal shape put in the "gate" of that ERS will be projected onto the stage. Usually this shape comes from metal adjustable shutters or an iris, but often the shape comes from etched stainless steel "gobos" also referred to as patterns or templates. If a lens of this quality were used in a Fresnel spotlight it would project an image of the filament which would not be of any use. So the Fresnel lens used in the Fresnel spotlight is crudely molded and further blemished with dimples or striations in the back of the glass thus making for a beam with a soft edge. He is correct to mention that adjusting the distance between the correct lens and the lamp will change the diameter of the beam. Two more things on this topic. The Fresnel lens on his table demonstrates one specific actual refinement of Mr. Fresnel and that is the black risers that you see. This blocks all light going through the lens except for light that will pass through the curve of the lens. Any other light will wash out the high focus of the lens. The other thing is that the Ellipsoidal Reflector spotlights (ERS) that used these lenses were referred to as "Stepped Lens ERS" spotlights which is unfortunate as they actually used Fresnel lenses like that on the table. I think they used the wrong vocabulary to distinguish from the crude molded glass Fresnel lenses in the Fresnel Spotlights. Some follow spots of the era WOULD use actual stepped lenses. For those who need to know the difference, with Fresnal Lenses, the excess glass is removed from the flat side and then the concentric rings of the curve are collapsed down to the flat side to make a flat lens but maintaining the exact curve that the lens would have had if it were not collapsed. A Stepped lens simply carves out the excess glass from the inside leaving the inside ends flat, so that the original curve stays intact. So a stepped lens takes up more space. It is not flat but at each point in the lens there still is a flat side and a curved side, just with excess glass removed.

[@carpballet]

As a theatrical carpenter I can say without hesitation that you are a pedant.

[@somercet1]

Awesome history, thank you.

[@Shinzon23]

*screaming* text wall! TEXT WALL! Why art thou not using paragraphs and punctuation?!

[@robertobradford3968]

You know what's the hardest part of being a lighting guy? Telling your parents that you're gay! I say this with love and respect, from a rigger to a lighting guy. 🤗

[@user-vp1sc7tt4m]

@@robertobradford3968 Are you for real or just trying to do stand up here. Your comment was inappropriate. If it was an off the cuff joke with no intention of harm, what's you explanation.

[@michaelogden5958]

A Fresnel setup in a lighthouse is one of the most amazing things I've ever seen. Not only technically fascinating, but aesthetically amazing.

[@mandolinic]

I had a reversing aid on a previous car. It was simply a Fresnel lens in the rear window, which gave a better view of the area immediately behind the car. Simple and cheap!

[@zachary3777]

How does that work? Wouldn't everything be out of focus

[@mandolinic]

@@zachary3777 It worked just fine. It was essentially a combination prism and concave lens, which was hung off the rear window and "looked" downwards behind the car to make reversing easier. Instead of being a single slab of glass or plastic, it was made into a thin Fresnel lens with the rings very close together. This made it very light (and cheap). The image quality was adequate for the purpose. I should add that the car was a hatchback. They're still on sale on Amazon UK (but not on Amazon US) for around £10.

[@user-ji8ls9dr9f]

Still have them on the transit busses I drive

[@mpatey63]

Oh I remember those ! We didn't have one and I wondered what they were.

[@geezer652]

I drove semi-trucks for 25 years and always had a 6"x9" fresnel on the right side window. Worked like a charm. And saved the lives of many an idiot riding along in my blind spot.

[@danielhathaway8042]

I work for a optical manufacturing company on the Oregon Coast. We helped with the repair and restoration of the lens at Hecate Head and Cape Blanco. It was done just before I started working for them. Talking with the Master Opticians they told me that it was very difficult and required a lot of hand work.

[@jliller]

The glass used in historic Fresnel lenses is very heavy and also scratches easily so working with the requires using very specific materials and cleaners, and great care in handling.

[@spikespa5208]

Heceta Head. IMO one of the most beautiful and dramatic locations for a lighthouse on the West Coast.

[@barneyduncan5811]

It’s spelled “Heceta”Head…

[@spikespa5208]

Oops. My bad misspell.

[@Orchardman53]

I remember visiting a light house (St. Catherine's, Isle of Wight, I think) where the staff showed us a large Fresnel Lens set/box (about 5ft tall) was floating on a liquid mercury bearing. He could turn the lamp assembly with a single finger. That was before the days when mercury vapour was considered dangerous.

[@jackx4311]

Fresnel lenses were also used for many years in the paraffin (kerosene) lamps used on British railways, in train tail lamps, signal lamps, and gate lamps on level crossings (grade crossings). The reasons the railways stuck with paraffin lamps for so long were ease of use on freight trains, gate lamps and semaphore signals which had no electricity supply, and on signalling lamps used by gurads and shunters (dry batteries in those days had *very* short lives); and the fact that the oil lamps could stand up to the battering they got, and stay lit Try standing near a semaphore signal when the signalman puts the lever back in the frame, and the 50 lbs or more counterweight slams down to put the signal back to danger! I was astonished, the first time I saw a train's tail lamp, with the wick cleaned and properly trimmed, and the small yellow flame shining through a red Fresnel lens. Even on a bright sunny day, the bright red light was clearly visible for several hundred yards!

[@AlRoderick]

The fact that the old kerosene lantern lenses got very hot and then shattered immediately when exposed to any source of water, like the rain, was the motivation for a glass company in upstate New York named after their hometown of Corning to develop a heat resistant form of glass. That's the origin of Pyrex.

[@jackx4311]

@@AlRoderick - you can learn something new every day, and thank you for passing that on. I only found out a short while back that the injector used on steam locos to force water into the boiler was originally designed by a French engineer - who intended it for use in a steam-powered aircraft! The aircraft never got beyond the drawing board, but millions of his design for injectors have been and still are in use on steam locos since then. I suspect there are very many other products in daily use which the inventors intended for a very different purpose.

[@kaitlyn__L]

@@jackx4311 you might know this one, but the adhesive that makes post-it notes work was originally a failed experiment for a strong paper adhesive. It was shelved, until product development at 3M came up with the idea of temporary stick-on bookmarks, and suddenly a really weak adhesive was called-for! That's basically an entire category of stationary (and furniture?) now.

[@jeffreyyoung4104]

I have one of the 'self stick' Fresnel lens on the rear window of my motor home for backing up. Without it, I was not able to back up when towing a trailer, and with it, I could steer the trailer without a second person directing me.

[@leswallace2426]

Just came across this channel and it's fantastic! I've known of Fresnel lenses for many years, but this is by far the best explanation of their history and use I've ever heard.

[@Waldvogel45]

I live about 330 meters from Fresnel,s house walk-- by it everyday, and our Townhall has a manificient lens on display. I am heartened by Prof Poindexter's comments since I am due for Cataract intervention within months. So now I know I have to thank Augustin again for his invention, and Prof Poindexter for the 100 % reassuring comments.I live in Mathieu, I have saied a lot at night on coastal navigation exercises and therefore directly benefitted at sea too.

[@KiwiCatherineJemma]

Fresnel lenses were also used behind the screen of those large screen, big boxy, "rear projection" TV sets. Back before flatscreen Plasma/LCD TVs existed, if you wanted about a 50 inch screen size, you bought one of those Rear Projection TVs.. They were apparently very common in the USA and for many years, as replaced by newer flatscreen TVs, often got dumped on the side of the road where USA folks can strip the Fresnel Lens approx rectangle 3 ft by 4 ft out of it, to use for various projects.. Here in New Zealand, those big TVs were always very rare and so consequently, very few have been dumped at and-of-life. Therefore the biggest Fresnel Lenses we get to play with here, are the A4 size ones sold at $2 shops. Except they've become unavailable years ago, and the biggest size I've seen for years, is now half that, at A5 size, and the shops' pricing is now $2.50c , $5 and $10. .

[@davidkohler7454]

Yes I have several of those huge plastic Fresnel lenses from projection tv,s.they are fun to play with and can be very dangerous if left anywhere a beam of sunlight can hit it. They will start a cardboard box on fire almost instantly when the sun beam is focused into a pinpoint. By slightly bending the lense you can direct the beam that way. I have busted concrete blocks with it and melted glass bottles into molding puddles pretty easily. It will boil water in no time. Was thinking about making a steam boiler with one. But you must track with the sun as it is moving. Pretty cool.

[@KiwiCatherineJemma]

@@davidkohler7454 The largest Fresnel Lens I have is the size of a standard A4 piece paper. Years ago I used to live in Rural Western Australia, (no air pollution, except for the dust sometimes) at about 33 Degrees South Latitude ("Mediterranean climate"). I remember one time I tried, not sure the exact time of year but I think it was about Spring or Autumn, ie NOT Mid-Winter NOR Mid-Summer. As an experiment I tried setting fire to a piece of crumpled newspaper. Anywhere near the middle of the day, while the second or two of trying to focus it to the smallest point, and the paper was already fully on fire. This alone was amazing to me, as like most science interested kids I'd had small magnifying lenses before, about 1 to 3 inches diameter and it took some time of focussing the rays to get something to smoulder and longer to get paper on fire. However that same day I also tried 2 other experiments. At about 30 minutes after Sunrise and also at 30 minutes prior to Sunset, so with the Sun just barely well clear of the horizon and any stray occasional trees in the distance, I tried the Fresnel Lens. It took a few seconds, but still started the paper burning very quickly both times. I've never managed to come across one of the larger lenses from a Rear Projection TV.

[@the123king]

a fresnel lens, in conjuntion with a diffuser, is found in nearly every modern LCD panel

[@leonardhirtle3645]

I just discovered your channel. I’m truly impressed. You deliver the information clearly and concisely. I’m looking forward to seeing more of your content. Thank you.

[@gwickle1685]

Well done. I saw a Fresnel lens at Cape Ann Lighthouse in Massachusetts twenty years ago and it has always fascinated me. That flimsy magnifier was a great bonus. Thanks.

[@erictaylor5462]

These lights are also used at most airports. At night airports use a rotating beacon. that projects a white light in one direction and a green light in the other. So from an airplane you will see a flash of white followed by a flash of green. For a military base the white light is split in to so the sequence is a double flash of white and a single flash of green. They also use something like what the carrier uses. Either 2 lights one behind the other, or four lights next to the other. If all the lights are red you are below the glide slope. If they are all white you are too high. If half the lights are red and the other half are white, you are right where you should be. The four light system can tell you if you are close when 3 lights are the same color.

[@j.d.farmer6164]

And the VASI light system at airports caused the production of a little training poem: White over white, too much height Red over white, just right Red over red, soon be dead

[@RoamingAdhocrat]

That's pretty much the same application as a maritime lighthouse

[@RJDA.Dakota]

@@j.d.farmer6164that’s good to know!

[@flybobbie1449]

Called Pundits and Occults.

[@TigerBoyRS]

Very rich and compact video about Fresnel lens. Such an interesting story, lots of detail. Cheers 🇵🇹

[@SofaKingShit]

I was going to write an attempt at a humorous comment but the level of creative genius and lateral thinking genuinely blows me away no matter how many times l see these lenses. Utterly amazing.

[@PaulinesPastimes]

A fascinating video. I love your channel. My 1960 Austin Cambridge has Fresnel lenses in the tail lights! Many older cars do, amazing. Now that I think about it, they are everywhere! Thank you Monsieur Fresnel.

[@senatorjosephmccarthy2720]

Really interesting info. Thanks for shining the light on us!

[@justincase5272]

Done right, NOT blurry. Both of my cataract replacement lenses contain fresnel components which result in dual-focus, with focal lengths set at infinity and about 30 inches, while also correcting for astigmatism. At distances between them, I still have 20/25 vision, but at both those distances, my vision is 20/15. Thus, I do not need correction for either driving or at the computer, where I spend 98% of my reading. A simple pair of 2.0 readers provides clarity for reading books, the newspaper, and the all too-fine print included with most products. I heard you mention headlights, but most headlights use a primary reflecting bulb within a secondary reflecting housing. I didn't hear you mention taillights, which I found surprising, as they're the number one use of fresnel lenses today, and are seen by every driver and ever passenger while driving at night!

[@oddball_the_blue]

Bravo on the pronunciation of Flamborough head - it's rare to hear a North American resist the urge to say "Flam-bu-row" rather than the correct "Flam-Bruu". Take that as thanks from a Scarborough native (about 20 miles further north of Flamborough head)

[@jonnyphenomenon]

Is Scarborough supposed to be provided scar-bruu? I am from Maine, the northeastern state in the USA, and we have a town called Scarborough, which we pronounce scar-buh-roh. (Actually, we kind of say scar-buh-roh. We also pahk the cahs in the yahd. )

[@usaturnuranus]

​@@jonnyphenomenonyep, also it takes three syllables to go to Scarborough Fair.

[@Longnose154]

what a wonderfully performed presentation. Well done sir! This channel is way underrepresented for the quality of content. I hope this changes soon and more people can enjoy the pleasure of learning cool stuff.

[@maxclark11]

Always fascinated by the Fresnel lens, but never new the history until now. Thanks

[@AZREDFERN]

Back projection TVs used massive yet thin Fresnel lenses. 60's to mid 2000's front projection headlights were Fresnel lenses with patterns. And all VR headsets until a year ago used Fresnel lenses as focusing elements.

[@nade5557]

This video was great to watch. The history, all the necessary info and not much more, some examples and cool uses in real life all presented with good pacing and visuals.

[@jacksemporiumofstuff]

I've always been fascinated by fresnel lenses. Great content!

[@btbb3726]

Very concise and articulate presentation! Thank You! 👍🏻

[@MetaverseAdventures]

Fresnel Lens are also in a lot of Virtual Reality headsets. I had no idea Fresnel Lenes had such a deep history. Thank for the video.

[@alanfenick1103]

Really enjoyed the explanation and usage of Fresnel lens. Always wondered how light was focused with the giant glass lens in lighthouses.

[@jackprier7727]

Thanks, once again a very very informative and interesting exposition of a LOT of aspects of light-projection-

[@jimkelley1000]

Mussorgsky - you are a Polymath. Thanks for your videos, they do not go unnoticed

[@Dannysoutherner]

Very cool! Thanks for making this, these lenses have always fascinated me.

[@alabamatechwriter6959]

A Fresnel lens is (was) included in the set of lenses that was part of an angled military flashlight for personal use. I never used the lens because I had no idea what it was for and do not think anyone else knew, either. Interesting! Thank you.

[@ypaulbrown]

wonderful program, thank you so much.....

[@victorherron2767]

Outstanding! I've seen a handful of your presentations (the one on crystal radios was my gateway), but this one prodded me to subscribe. Well done. BTW, I have a plastic fresnel exactly like the one you show near the end and have at various times carried a credit card-size version in my wallet. Even in the digital age fresnel lenses remain useful tools. Best wishes.

[@josemoreno3334]

Now I know the history of the Fresnel lenses and how they work today. Thank you for that great information. Great video lesson 👍😃

[@wouterke9871]

Fascinated by glass Fresnel lenses, and I think this is the best video I have ever found, thx.

[@justinmaitland7335]

I believe I have stumbled upon a hidden treasure in your channel, keep up the amazing work good sir! We truly stand on the shoulders of giants, and we are ignorant of a vast majority of them.

[@retired06]

❤That was a great presentation for a general audience of which I am part of. Thank you for all your efforts and applied skills in assembling and presenting it.👏👏👏👏

[@martykopka]

Really suprised how interesting this random channel that popped up in my feed was. Good Job! I hesitated to even whatch this video as I didnt know the channel and it seemed like a low number of subscribers, etc. Im glaad I did. Really interesting and well presented information. Congrats on a great job well done! Wil definately watch future (or past episodes).

[@Tag-Traeumer]

Fresnel lenses are most commonly used in PIR sensors, in the orange flashing construction site warning lights and in all sorts of signal lights, such as the classic starboard and port lights of boats.

[@MountainFisher]

I remember that in my engineering classes about warning lights. They even went into submarines.

[@Tag-Traeumer]

@@MountainFisher Interesting that submarines also have to have navigation lights. These must be pressure-resistant, perhaps they are filled with oil.

[@MountainFisher]

@@Tag-Traeumer The glass is several inches thick. Subs don't go down to extreme depths.

[@Tag-Traeumer]

@@MountainFisher Yes, submarines are not submersibles and dive a few hundred meters deep, i.e. a maximum of 50 bar, 725 psi. Filling with oil would relieve the strain on the housing and glass, but the optical properties of oil would make it difficult to focus light, which is the purpose of Fresnel lenses.

[@pierremainstone-mitchell8290]

Most interesting indeed! I've had dealings with Fresnel lens in stage work and with a rather indirect contact with the Cape Otway Light Station here in Victoria, Australia and it was very interesting to watch your video about them!

[@JCO2002]

I've wondered how those things work for years. That was great, thank you.

[@ysgoh1981]

Very informative and easy to follow, Thank you!

[@EarlWallaceNYC]

Thanks for a very understandable and insightful review.

[@JC-jv5xw]

In the theatre/film light from which your lens came, it is normal for the lens to be fixed at the front of the fitting, and for the lampholder/reflector assembly to move inside the fitting to adjust the beam width. When the lamp is near the lens it gives a wide beam and when further away a narrow beam - in which case some of the light from the lamp and reflector never actually exit from the glass. This may seem bizarre compared with the simpler arrangement of having a moveable lens. But the wide beam angle can be as much as 60 or 70 degrees which could not be achieved if the close lamp-lens setting was produced by retracting the lens into the housing - where the housing itself would restrict the beam. The fresnel light is used because it has a softly focused, diffuse beam with no hard edges, which makes it much easier to merge and blend the light from multiple instruments. Normally used for short throws such as over the stage. Its opposite is the profile spotlight which has a normal convex lens and produces a well focussed hard edged beam. These are usually produced with much narrower beams and are typically used for longer throws from the auditorium. Consequently these use the simpler arrangement of a fixed lamp and a moveable lens or lenses.

[@misterbonzoid5623]

An elegant explanation. I work in theatre and my favourite generic fixture is the zoom profile, which is incredibly versatile and of course, like the fixed-angle version, allows the use of gobos.

[@clarkgriswold5842]

Love this channel, a true treasure trove

[@minkymoo4794]

A++ Very interesting. Love this kind of stuff.

[@barryjewell4511]

Impressive presentation, very good job!!

[@stevenbrown7042]

The plant I work in uses many lights of different colors to indicate varying conditions of the machines. The lights themselves use fresnel lenses so a small low cost effective light can be mounted 30’ in the air and be seen across the floor of the line clearly. It makes my job easier by looking at the light, hearing what alarm sound is going off and a quick visual of the machine I can have a good idea of what went wrong and make it easier to correct.

[@Seiskid]

Whilst they were never ever "used in headlights", they were common for tail, indicator and brake lighting in most cars build from the 1940s to the 1980's. In the mid 80's parabolic reflectors became more fashionable. If they were designed well (and not all cars were) they made for really good, bright, clear lighting.

[@transtubular]

Indeed! Automotive head lights in the US at least, had rather complex lenses that were designed to project the light in a particular way so that oncoming drivers were not blinded and the side of the road was more illuminated.

[@Anvilshock]

Just because they may never have had a full uninterrupted Fresnel lens as such, the sections still followed the principle of some arrangements of staggered prism rings or ring segments, so, the use of the name is still valid.

[@kaitlyn__L]

@@Anvilshock also, the modern headlight lenses still have various concentric/parallel patterns etched/moulded into them to improve the focusing of the light spill. It's one reason you can't just swap out the actual lamps and adjust their distance to be looking mostly right for the new ones, the focus and edges of the beam are still going to be wrong.

[@markwarren7157]

Great video! Very informative and well presented. I am a fan, I subscribed and will watch more.

[@kyleeames8229]

When I was in elementary school, overhead projectors were very common. These used fresnel primary lenses to columnate light through a transparency and focus it into a secondary below a mirror, allowing the teacher to display prepared materials on a whiteboard or screen during lectures. Beginning in high school, these were phased out in favor of digital projectors and by the time I graduated, I don’t think my school even had these devices anymore.

[@MountainFisher]

columnate=collimate; Sorry I was a teacher during COVID and was good at it. Kind of surprised me, who knew? I have reflector telescopes that must be accurately collimated to acquire the best focus. Hubble and Webb are both reflectors. Those diffraction spikes are irritating and actually block part of the view. They are called _diffraction_ spikes for a reason, they diffract the light waves coming off bright pinpoints. Some of the Webb's raw photos are a disappointment because of the massive spikes they generate, but they use Photoshop on many publicly released photos to show what they know/presume they're obscuring and they are correct to do so. I have access to a 24 inch reflector telescope through my astronomy club, but to get to it is another story. Yet on a clear night you can see many Deep Sky Objects (DSOs) that with smaller telescopes you need long exposure photography. Still it has those diffraction spikes, but not nearly as bad as with a camera that can pick up more light waves than a human eye can.

[@rogeriodinizmachado3734]

thanks for sharing, great and clear video

[@dvoiceotruth]

Had been a fan of Augustin Fresnel. Didn't know this before. Thanks.

[@jetsons101]

Great watch. Boy we can learn something new every day............

[@antonnym214]

Excellent. Very interesting presentation. I subscribed immediately. Thank you!

[@ableone7855]

You have a great channel here. Thank you for the great and interesting videos. 😊

[@StarchildeX]

I was a docent for the Golden Gate National Recreation Area and I lead tours to the Point Bonita Lighthouse at the mouth of the Golden Gate. It still has a functioning Fresnel lens installed. I used to have to share anecdotes about the lens. Great history lesson!

[@rikardlalic7275]

Top-level lesson!

[@telugumisimi]

Thanks so much for the deeply informative video!

[@shinola228]

Very interesting. Thanks for posting.

[@pedtrog6443]

Another piece of information I didn't know I needed to know

[@ericpierce3660]

Thank you, that was fascinating.

[@josephrogers5337]

also used in overhead projectors used in school class rooms.

[@the_black_douglas9041]

Excellent! As a filmmaker, my focusing fresnel light attachment is an indespensible tool. I had no idea of its fascinating history!

[@caseyrevoir]

The technology progression to rotate and regulate the speed of the lenses is really neat too. Those lens assemblys were floated on Mercury which affected the workers.

[@EricLehner]

The internet at its best. Thank you to contributing to human wisdom. Cheers from Canada.

[@lkp7481]

I live on Abaco in the Bahamas where the lighthouse in Hope Town on Elbow cay still has from what I can understand the last kerosene manually operated lighthouse in the world using these lenses for historical and tourist reasons. It uses weights to turn it and still has to be cranked up multiple times per night by a lighthouse keeper and still has all the original mechanisms from the 1800's or duplicate newer ones. It is pretty cool to see. It should be on the bucket list for any lighthouse enthusiasts.

[@koyotekola6916]

Excellent, informative video. I've heard of Fresnel lenses, but I was pronouncing their name wrong. Their applications are very interesting. Thank you for yet another great video!

[@jamesslick4790]

I always wondered how/why Fresnel lenses worked. Cool Vid! 👍😊👍

[@nigelappleton2963]

very informative and enjoyable

[@guidetheride2103]

Fascinating, thanks

[@CreativeWarrior-]

Great channel!

[@004Black]

A little late to the dance, but I was stationed on Seguin Island Lighthouse which sported a fixed first order fresnel lens and a 1kw halogen lamp. The beam was visible for up to 25 miles out to sea, depending on atmospheric conditions. It was a continuous polishing process to maintain optimal function.

[@ZheDong]

Nice video man!

[@iforgetiremember5243]

i'm coming into the video with 0 knowledge of lighthouses or their tech. i still thought it was fascinating though. 10/10 presentation, _all killer, no filler_

[@kentstray1]

Fantastic content! Thank you so much!

[@robertivins6117]

Wonderful Exposé 👏

[@dwiggang4290]

@13:77 - Thomas Stevenson, one of a family of civil engineers, had a son who what a bit of a black sheep of the family. The son was Robert Louis Stevenson the author instead of following in the family engineering business.

[@michaelfox7756]

Subscribed! Where have you been all my life! Love this content. As I was watching I remembered the old Model T tail light I inherited from my grandfather. I went and got it, and sure enough Fresnel lens.

[@stevenikitas8170]

Great video, very interesting...

[@TheRealLink]

Very cool video! Heard of the lens type / name before but wasn't sure what it was all about. Thanks!

[@rc-fannl7364]

Interesting story. Btw, around 10:17 the graph shows 182.5mm but you say 1825mm

[@getyerspn]

exactement

[@Perktube1]

"If you recall your elementary calculus… " Uh,ha, that's a good one.

[@benoitbusseuil5518]

very interesting, you just got a new subscriber! thank you!

[@jackhreha4907]

Thank you for the great show. You have vindicated my junk box and it will save mankind. Best Regrds Jack.

[@secretagent86]

Fascinated. You earned my sub

[@petera1000]

Very interesting, thanks.

[@Siskiyous6]

The 8 Foot high Fresnel Lens from Point Saint George Light (activated in 1892) is in the Del Norte County Historical Society's museum on H Street, in Crescent City CA, it is art. If you have a chance to see it take the time.

[@tedk2814]

Thanks so much for sharing your knowledge about the Fresnel lens. I am a photographer so I came across a special lens manufactured by Nikon. It was a telephoto lens and in using the Fresnel lens science, these telephoto lens were able to be much lighter in weight. Ted in Sebastian, Fl.

[@Me2Lancer]

When I served aboard the ship during the mid-1960s our hand-held signal lights used Fresnel lenses. Later on, I had a video production studio and had several Fresnel lenses.

[@slevinchannel7589]

IF i timetravel: should i take money for the Lens Craft-Recipe and if so how much?

[@billedos]

That's so crazy. I work lighting in theatre, and I never really thought about the lenses being used elsewhere