We're so used to seeing lens flares that video game graphics spend considerable resources to recreate them in modern games, even though there's no lens involved there at all and no reason for them to exist.

One thing I like about lens flares is that you can see just how much work the image stabilizer is doing, since the flare can be jumping around quite a lot, while the main image remains quite steady.

I see many complaints about digitally added lens flare here, but there is actually a good reason for why it exists: Because it effectively communicates that you are looking at something very bright, even if your monitor isn't capable to display that much brightness. This also allows you to continue to use some more dark colours without losing the subjective impression of that the scene is brightly lit. Which is useful, because making the image brighter as a whole will lose you detail. If you can only use numbers between 50 and 100, then you have fewer different options (=less detail) than if you can use numbers from 40 to 100. And finally, it's just not possible to give you all the visual effects that your eyes create when they're looking at an actually bright scene in real life. Lens flare can serve as a stand-in for some of these other effects.

I'm a lens designer. Very happy to see some optical engineering content on this channel. This is a quote from the preface of my go-to Stray Light textbook (E. Fest, Stray Light Analysis and Control). 'In 1741, the great Swiss mathematician Leonhard Euler was asked by King Frederick the Great of Prussia to write a tutorial on natural philosophy and science for his niece, the Princess of Anhalt-Dessau. Euler agreed and began writing the tutorial as a series of letters to the Princess, about one a week, for nearly 250 weeks. These letters were eventually published as a collection and became some of the first popular science writing. In a letter entitled "Precautions to be observed in the Construction of Telescopes" (shown in the second figure), Euler recommends that the Princess ". . . (enclose the telescope) in a tube, that no other rays, except those which are transmitted through the objective, may reach the other lenses. . . If by any accident the tube shall be perforated ever so slightly, the extraneous light would confound the representation of the object." He also suggests that she "[. . . ]blacken, throughout, the inside of the telescope, of the deepest black possible, as it is well known that this colour reflects not the rays of light, be they ever so powerful.'" Amazing that we've been collectively observing this phenomena for hundreds of years, and the mitigation techniques for it are largely unchanged since then.

Something that's fascinating to me is that we've become so accustomed to seeing lens flair in video and images that we replicate it in CGI to increase the realism even though removing lens flair would represent a live scene better.

fun fact: some lens flares are actually the reflection of the sensor in the rear-most element, so even if lenses are very good at eliminating reflections, some cameras have particularly shiny sensors the lenses weren't designed for.

In animated shows and movies, the animators often add lens flares especially for shots of the sun, despite the fact that they're "not supposed" to happen. This is because people have gotten so used to seeing them in videos that the lack of it feels off. It's such a happy accident that people go out of their way to make it happen as a non-accident.

Man, I missed u so much :)

I tried to put my hand behind the sun, but to no success. Then suddenly, half a year later, I succeeded even though I wasn't doing anything different :P

One of the more unusual uses of a toonie, but it did the job, so this Canadian approves.

It feels like it's been a long time, since I saw Minute Physics video. Great as usual.

There was a partial eclipse in my area a few years ago and I could see it in the shadows of the trees. The leaves of the tree made several thousand pinhole cameras, which all of them looked like the eclipse (though I couldn't confirm this by looking at the eclipse directly).

The takeaway from this video is: Always use a hood on your lens, even if there are no visible bright sources in the image that might cause flare. Not only does a hood reduce even indirect light hitting the front element of the lens and causing flare and other problems, it also protects the lens, as it creates a physical barrier between the first lens element and the scene, making touching, hitting or scratching the lens much less likely.

We've been so accustomed to lens flare in digital media that lens manufacturers started to market such defect as a feature. Sometimes even intentionally design the lens to actually have flares

I'm so happy you're still making videos. I used to watch every new video in hs and my early 20s. Nice to know you're still here.

Thank you for a very informative video. Some others could have made a one hour video with the same information; you managed to compress it down to 5 minutes. Impressive!

Time and Date has great eclipse calendars, and you can also use Stellarium to view the solar system (and stars etc) and advance/rewind time. I couldn't catch the last eclipse, but I could view it in Stellarium afterwards. Wasn't as impressive, but still fun to do.

Nicely diagramed Tessar!

Great video, entertaining script, especially at the end!

I wasn't able to photograph the eclipse so much as I was able to capture a very nice lens flare of the eclipse.

cool, concise, competent. Well done.

Optical engineer here who works on space optical instruments. We call these flares "straylight" and it is a massive pain in the ass. While the simple cases are easy to model, most straylight is very complex and difficult to predict.

I hope game devs who feel the need to add lens flare and chromatic aberration to their first person games see this.

Once during a partial eclipse, I was in some boring business meeting. The sun was strong, so blinds (Venetian) were down. They had a lot of vertically lined holes for support lines, so small rays of sun did pass through, and some of them were falling on table in front of me.. Looking at those rays suddenly I realised they had shape of eclipsed sun, something I never seen before. They were not just rays, but a projections of sun made through holes acting as pinhole projectors, and there were a bunch of them in room. I was so excited that I had to interrupt someone to share my discovery with others.

great video as always

I got a few photos like this with my phone, what an awesome accidental science lesson on top of the already extremely cool science moment, the eclipse itself

You wondered if the flares were the shape of the lens element or the aperture, and you could actually see the shape of the aperture in the flare as it moved across the frame. There's a perspective shift that happens relative to the position of the light source that causes the aperture to take "cat's-eye" shapes towards the edges of the field of view (similarly how your own pupil would look if viewed from a side angle, you're essentially viewing a circle from the side, causing it to become more oval in shape).

Awesome video, thanks.

This was very well explained, thanks!

Good episode. 👍

I am actually surprised U're still alive and actively uploaded on Utube. Thanks for Excellent Works!!

that line at the end about putting your hand behind the light source which also gave you a reason to move your hand there to to turn off the lamp was so elegant! the dual purpose was a work of art!

0:00 Did not know you were from Canada. Hi fellow Canadian from Montréal (QC)

What I find interesting is that we are so used to seeing lens flares from the sun that they are often included in animated movies, at least in scenes that draw attention to the sun

Very interesting, thanks a lot 👍

You can also get flares inside your own eyes (or at least I can), when you look at a strong light projector you can see a rainbow around it (and probably other circles as well) which is a diffraction flare of the human eye.

I just remembered what these videos remind me of. Blue's Clues, when drawing the clue. With the low bass in the background and the drawings, etc. fun stuff.

It's neat how different lens geometries and materials produce different shaped flare spikes. Aluminum oxide in deep IR makes triangular flares from certain sensors too

1:04 jup, jup it is. But also fascinating!

Another fun fact - flares help to recognize stabilized (in post) footage, because the light source is stable and the flare isn't.

Thanks

A video of information, This is great

i genuinely got an amazing laugh out of everyone going: "AHA SEE?! this is proof of

great video

Please. I need more uploads!

1:50 didn't expect that jump scare

This seems like what we see in all those military UFO videos. Except I think it's the parallax reticle being out of focus we're seeing in those UFO videos.

Best teacher on youtube

didn't JJ Abrams perfect the lens flair? :D great video as usual Henry. I hope the rest of the family is doing well

Could this happen while wearing glasses? Or are the eyes to close to the glas for you to notice it?

If I look at a bright led and just squint, it recreates an interference pattern in the flares.... neat!

Well, that was fun. Good job.

So cool, i never question those

sometimes lens flares add depth and make for really cool shots intentionally, but having it work on eclipses is even cooler!!

The explanation of why the flair is green in your examples is really interesting. (Hint: the sensor of cameras that use Bayer patterns looks green)

I didn’t know minutephysics comes out of Canada. The two-dollar moon tipped me off. 0:01

How I have missed minute physics, it is one of the very few channels I am actually subscribed to.

We are so used to flares in images that video games program them into their rendering when it shouldn't even be there. They make extra effort to make it look realistic.

So cool that you can see sun spots at 3:08 without a proper solar filter to see them. I was expecting them to be drown out on the flare.

1:40 Human visual system response is logarithmic. So 1% light passing is just 25% less bright than 99%. Not 1% as bright...

Hello old friend, welcome back

I recently got a really clean photo of an eclipse through juuuust enough cloud cover. The blue halo around it is a very interesting visual effect.

AMAZING video on the subject, "What is bloom? (And how is it simulated?)" (2021), talks about how to simulate real artifacts like glare in cameras.

can you do a video on how glass is made into lenses? I imagine there's a heating and shaping element as well as molecular chemistry and doping involved too as well as machining machines to do some grinding.

welcome back!

A minutephysics video! Yes! Ah, for those days of eld when many such videos were published. Perhaps they will be again, one day.

I didn't want to buy a solar filter for my camera, so I just stacked 4 layers of car window filter, and it worked.

Welcome back

I personally really like how lens flares look. Also, most 3D games with light scattering implement it even though there's no reason to... aside from looking good.

It's so funny how camera people try to make lens flare go away, and computer graphics people try to add it.

I was in Canada in 2017 so we just had a partial eclipse. There was cloud cover but thin enough that the sun was dimmed just enough that you could look at it and get good pictures from just a phone camera

*As someone who Got into Indie Filmmaking & VFX/Compositing back when the First JJ Abrahams Star Trek came Out i feel called out as would my entire group of friends at the time probably upon seeing this* 😅 *We went ham on the Flares and i had to kick my Lens Flare Addiction JJ Abrams Gave My Indie Film Making Circle.* *Now as a Designer I'm Addicted to Bloom & A Level of Saturation that would make Doctor Who Throw Up.* *To be fair its inspired by that 2000s Era of Games like Oblivion back in that "Bloom & Color" way.* *Amazing Work & Super Informative Video!* ✨ *I will actually be using this video to try and test doing some more realistic shots jus because i wanna see the difference now that i know* *Truly I feel quite dumb for never realizing this although I've never even handled a camera with an adjustable lens due to budget constraints* *Wouldn't have gotten good at VFX & Compositing if i could afford to do anything* 😂 *You Rock* *Please Take my Like & Sub!* 💕 🙏 Edit : *Apparently I Was Already Subscribed...* *They All Blur Together after a While*

I loved how you used a toonie :)

I felt that the video should also have explained that the lens flare always appears on the opposite side of the optical axis of the lens, so that a line drawn between the actual light source and the flare always passes through the optical center of the image (this is of course not true for tilt/shift lenses or for many cropped images).

The brightest thing is why cinematographers use lens flare. The flare emphasizes and illustrates the brightness of a light source, because movie screen can only get so bright.

I expected an explanation about why those kind of flares usually appear mirrored from the center of the image. It is funny that some people embrace flares to show off their anamorphic lens for example.

I like that you don't have to watch the video to get the answer as everything you need to know is in the thumbnail. Thanks!

A toonie!? I think thats the second coolest part of this video!

I'm JJ Abrams and I approve this message.

Hi Henry!

Don't stare at the sun unless you are a stable genius.

can you please explain how aperture affects depth of field in camera in terms of mechanical?

"which, with the sound at least, is kinda of hard" Me: is that a challenge?

The phrasing in the script sometimes is funny. I know it’s supposed to mean “unintended” or “undesired”, but when Henry says that light "incorrectly reflected or difracted”, it sounds as if he’s saying “the light didn’t obey the laws of physics” 😄

A Lens Flare is when you put cute stickers on your camera

I think it is really weird how when playing a computer game, you often see in-game suns with lensflare

nice twoonie!

Awesome

Super cool indeed.

One of those lens flares-as you moved it across the sun-seemed to indicate a bowl-shaped flare cupping another flare. It's that caused by the camera? I've seen during one eclipse decades ago that light shining through the trees hit the ground in "C" - shaped crescents, just like on my pinhole cards. The edges of these tree leaf aperture were also made up of crescent-shaped lights, even though the light on the ground seemed to mirror the shape of the aperture it came through. I could put my hand between the light and the ground and block it. I'm assuming even the camera obscura I made as well as the leaves caused the little crescents on the ground even as waves were bent at the edges of the aperture. To see the flares, I assume you have to look back through the aperture to see the light bounced off the aperture.

at 3:10 you can see a sunspot in the projected image of the sun. Nice

no, that's just a windows loading cursor. someones pc is lagging

Very cool :)

At 2:00: I love how there is a rainbow-color🌈 in the lens flare.

I suppose I can use this to test it.

The last few seconds is how I tell apart the original image and astigmatism 😅

I've been using glasses for decades and only now realized the lights I used to play with as a kid are the same as lens flare.

Hi, I just watched your video about what would happen if a portal went through another portal, and I had a follow-up question. What would happen if you were to jump into the point of the portals intersecting?

1:45 1% is a non insignificant amount when we talk about light you will definitely see it

Whoa!