But What IS A Lens Flare?
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- Опубліковано 5 гру 2023
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A lot of people took pictures of the recent solar eclipse in North America and got photos where there’s a ghostly image of the eclipse floating in the sky nowhere near where the sun is!
REFERENCES:
Lens flare prediction based on measurements with real-time visualization doi.org/10.1007/s00371-018-15...
Physically-Based Real-Time Lens Flare Rendering doi.acm.org/10.1145/1964921.19...
From the Series of Articles on Lens Names: Tessar, by H. H. Nasse. Carl Zeiss Camera Lens Division March 2011
www.cambridgeincolour.com/tut...
www.toolfarm.com/tutorial/in-...
petapixel.com/what-is-lens-fl...
www.maxon.net/en/red-giant/vf...
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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.
That, and chromatic aberrations, which is insane, as our eyes don't have them. Most games are from meant to be the view out of the player character's eyes, after all.
Yeah I noticed that about GTA5. It was very realistic driving towards the sun 😆
@@mytube001I hate that so many games have chromatic aberrations and film grain enabled by default, because these effects are often greatly exaggerated compared to modern cameras
Lens flare are understandable tho, they look cool, and kinda recreate the feeling of really bright lights.
Chromatic aberration is just ugly
Videogames aren't trying to pretend to be a perfect recreation of someone's eyes, they are creative projects that throw in impressionist elements to look good and make you feel something within the limits of a screen
You might see rain drops on a first person view despite rain drops not being possible on human eyes, this is a way to invoke the sense that the character feels rain on their face.
You might use chromatic aberration to invoke the feeling that it's hard to look at something, or film grain to give a sense of paranoia of shadows
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.
Same deal with reflections, such as on your phone screen. The movement is amplified so that imperceptible motion becomes perceptible.
LensFlair likes you too
Woh, good catch. That's cool.
As far as I know (studied electronics ~20 years ago -didn't practice it😢) the stabilizer steals pixels from the edges as to compensate if you move a bit. I remember having a camera with a stabilizer switch on the menu, and when i would turn it on the resolution would drop.
@@sadderwhiskeymannfor optical stabilisation, the jumping flares are generally less apparent
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.
69 likes... nice
Also, we've been trying better lenses and blacker blacks(paint)
I guess that was the 18th-century equivalent of the six-pointed spikes from the JWST. Some things stay the same.
Unless you're Anish Kapoor@@catvamp100
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.
Would it? It might just be my eyes, but when I focus on a bright light from far away, there's usually a tiny spiky halo around it. Not as big as a lens flare from a camera, but a lens flare nonetheless.
@@a52productions
thats a different effect than lens flaring, but is something minutephysics has a separate video on (from 9 years ago)
for the curious: ua-cam.com/video/VVAKFJ8VVp4/v-deo.html
@@a52productionsYou probably have minor astigmatism
@@KaitouKaiju yeah, I also have it.
@@a52productionsThat's either astigmatism or you're perceiving the reflections of light off your own eyelashes (I'm not crazy, that's an actual thing).
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.
no, it does not communicate that, it communicate that the graphic designer was an idiot, same as head bobbing communicate that they never walked in their life.
@@thorin1045You're right, lens flares - which occur when a camera is pointing at something very bright - does not convey that the object it is pointing at is very bright! You're very intelligent. :)
Man, I missed u so much :)
4real
4real
Parasocial relationships are not healthy.
4real
4real
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.
that's one of the reasons why old lenses designed for film cameras don't work very well on digital cameras, because they reflect too much light that comes from the sensor.
That’s also why these look green - it’s the color of the sensor.
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.
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
Just remember to keep a distance so you don't burn yourself.
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).
I believe you. The curtains in my bedroom once made a pinhole camera. At night I could see a "bright" circle on a cupboard. It was only when this happened again at daytime that I realized that I had seen the moon and the sun.
So that's what causes that! I was confused because shadows don't look like that.
One of the more unusual uses of a toonie, but it did the job, so this Canadian approves.
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
Nicely diagramed Tessar!
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!
great video as always
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.
Great video, entertaining script, especially at the end!
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.
Could this happen while wearing glasses? Or are the eyes to close to the glas for you to notice it?
it does happen, especially at night or if you've had the lenses for a while and they've gotten a bit scratched
As a wearer of fairly thick glasses, this does happen fairly frequently (if you look at very bright lights), and is quite annoying, especially when driving at night lol
I've seen something like this happen when watching movies in 3D. When you put the 3D glasses at the right distance (3-4cm or ~1.5 inches) away from your eyes, basically resting on the tip of your nose, you might see a magnified and sharp image of your own eyes.
I guess you could call that a lens flare since it's an unintended reflection. It looks super interesting since you can easily focus on the image because it's somewhat magnified, and you can clearly see your own iris. Try this the next time you get to wear them (the light has to be dimm though, just like in a theater room).
Yes, I do have some sort of flaring when looking at light sources, or having bright light sources on my sides. I see them wearing my glasses but I do not when I remove them.
VR Headsets also have issues with different artifacts with the lenses, like flare and also godrays when using fresnel lenses. These are most notable when looking at white text on a black background.
Even your Cornea in your eyes creates visual errors similar to flare, most notably for people with astigmatism.
Yes a litte I think but not nearly so much as with camera lenses because a glasses lens is just a single piece of glass, with coatings. A camera lens often has several pieces of glass so chances to make reflections.
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!
cool, concise, competent. Well done.
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
I am actually surprised U're still alive and actively uploaded on Utube. Thanks for Excellent Works!!
I hope game devs who feel the need to add lens flare and chromatic aberration to their first person games see this.
Why?
Most game devs that add lens flare and chromatic aberration is aware that it is a "fictitious" effect.
They are adding it for theme and vibe, giving a more cinematic look.
didn't JJ Abrams perfect the lens flair? :D great video as usual Henry. I hope the rest of the family is doing well
I cant say anything about Henry but I'm doing great thanks for mentioning me! haha
I was hoping someone would bring this up :) Makes me wonder if there are lenses engineered for dramatic flairs :)
Honest Trailers!
JJ Abrams & 80s films love lens flare! 😎😎😎😎😎😎😎😎😎👍👍👍👍👍👍👍👍
This was very well explained, thanks!
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
I wasn't able to photograph the eclipse so much as I was able to capture a very nice lens flare of the eclipse.
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).
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.
whatever you guys have been doing lately on these new mirrorless lenses has been absolutely spectacular though. Keep up the amazing work!
Question from a RF engineer - I've always kinda interpreted all these effects as deterministic - is there (given sufficient dynamic range) no option to 'calibrate' out the lens flare?
Though now that I think about it, you can have lens flare from an object outside of your actual image field, which you wouldn't have sufficient information on with which to do a 'reverse lens flare' operation, so I guess I answered my question for myself?
Good episode. 👍
Another fun fact - flares help to recognize stabilized (in post) footage, because the light source is stable and the flare isn't.
really?
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.
Please. I need more uploads!
0:00 Did not know you were from Canada. Hi fellow Canadian from Montréal (QC)
How I have missed minute physics, it is one of the very few channels I am actually subscribed to.
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.
Awesome video, thanks.
sometimes lens flares add depth and make for really cool shots intentionally, but having it work on eclipses is even cooler!!
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.
1:04 jup, jup it is. But also fascinating!
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)
Well, that was fun. Good job.
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.
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
i genuinely got an amazing laugh out of everyone going:
"AHA SEE?! this is proof of
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.
Very interesting, thanks a lot 👍
A video of information, This is great
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.
So cool, i never question those
A minutephysics video! Yes! Ah, for those days of eld when many such videos were published. Perhaps they will be again, one day.
Hello old friend, welcome back
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.
Thanks
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.
can you please explain how aperture affects depth of field in camera in terms of mechanical?
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).
t/s lenses are no different in this regard. The correct explanation would be to further detail that when a t/s lens is shifted that you're simply seeing a reframed part of the image, but the actual effect remains the same.
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.
Welcome back
If I look at a bright led and just squint, it recreates an interference pattern in the flares.... neat!
Best teacher on youtube
welcome back!
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
great video
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?
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!
I loved how you used a toonie :)
1:50 didn't expect that jump scare
*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 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.
Don't stare at the sun unless you are a stable genius.
I didn’t know minutephysics comes out of Canada. The two-dollar moon tipped me off. 0:01
1:40 Human visual system response is logarithmic. So 1% light passing is just 25% less bright than 99%. Not 1% as bright...
Yeah, but it is still only 1% as absolute bright, in terms of luminance.
sensors are not logarithmic in response. A log curve needs to be applied to give a resemblance to human vision. Also, the 1% figure had nothing to do with relation to vision; 1% transmittance is a measured valued in relation to the strength of the source. It would be improper to curve it in relation to human vision with respect to lens design. The closest relationship you get would instead be a "t-stop" value.
It's so funny how camera people try to make lens flare go away, and computer graphics people try to add it.
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.
A toonie!? I think thats the second coolest part of this video!
Hi Henry!
What about the eye of the observer? How would that play in lens flares?
Do you want to hear an amazing great tidbit I discovered on my own when I was around 20…
So there was a partial eclipse here in France and I was taking pics… whatever. But when I went back inside I noticed the light from the part-eclipsed sun was shinning through the leaves of a tree, as it does… BUT the patterns on the floor were croissant shaped!!! It led me to understand that the usual shapes on the floor aren’t a projection of the leaf holes but rather a pinhole photography of the sun’s shape!!! Usually round, this time croissant…
😅 amazing.
My favorite graphic design professor, who was also a professional photographer, lamented that even though the folks in his field had worked assiduously to prevent lens flare in their work, Adobe came along and added the ability to put artificial lens flare into Photoshop images. He advised us to never use it, but qualified it as his personal opinon, not a design edict. I thought of him recently while playing Final Fantasy XIV Online and coming across that game's own implementation of lens flare, which shows up when aiming the view close towards the star near sunrise or sunset.
He would also probably tell you to never refer to him as a graphicS designer. Though there absolutely is a use for a lens flare in a graphic design sense. A lens flare gives an immediate impression that something is for example shiny, and therefore clean. This is probably why he didn't mean it as a rule but just something he personally doesn't like due to him being familiar with the other field. Seems like a good teacher for clarifying that.
It's better to be able to add it when you want it than to have to constantly find ways around it when you don't. Flare is often accompanied by glare, which creates a wash of loss of contrast across the frame (easily seen in a lot of this video, though not explicitly depicted). It's that loss of contrast which is the most important aspect of flare control.
Oi, an artifact of posting half-asleep in the wee of the morning. "Graphic design," indeed.@@TunaIRL And yes, he was a very good mentor -- I'm just sad I wasn't more into photography, because I'm sure he would have been delighted to teach more tricks of that trade.
"which, with the sound at least, is kinda of hard"
Me: is that a challenge?
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.
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.
Does that apply to "sunbows" too? Not the ones you can see with your eyes in the sky, but the ones that show up in a picture when there isn't one you can see with your head-orbs? On occasion I've had pictures of the sky turn out with really intense multicolor halos around the sun, even though there wasn't one to be seen, or anythign in the sky like clouds to cause one...
maybe those are somehow caused by bloom
OMG 😊 ❤ i did this during the eclipse hehehe It was fun ^^
I think it is really weird how when playing a computer game, you often see in-game suns with lensflare
I want to know more about rays that come out of light sources in photographs.
Does anyone have some good search terms what what I'm talking about?
I hear that it's based on the number of blades in the aperture.
A 5 blade aperture will make 10 rays because it's an odd number and the image is reflected.
While a 4 blade aperture will just have 4 rays. Is that correct?
I think these are generally called sunstars. Search "sunstar camera".
different lenses have different aperture designs. Some have curved blades which create a more circular iris, which actually helps to eliminate "starbursts". If an aperture isn't designed with curved blades, they will sometimes add more blades to attempt to create a more circular opening. Each intersection of each blade creates an opportunity for a starburst spike to form, with more pronounced edges creating more pronounced spikes (like on the JWST for example). I can't definitively say whether the "double the blade count" rule universally applies.
@@Rwdphotos Thanks. So the starburst spikes are usually an effect of aperture blades but not always.
Searching around it seems that "diffraction spikes" is a common name for this. I'm wondering if I will ever be able to look at a photograph and know definitively what caused the spikes. Is there a bottom to this rabbit hole?
@@Rwdphotos Is it always the corners of two aperture elements that cause the starbursts? I always imagined it was the edges causing diffraction that results in the starburst.
A Lens Flare is when you put cute stickers on your camera
I suppose I can use this to test it.
nice twoonie!
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” 😄
here's a question: how come during a partial eclipse, shadows are also cast in the shape of the eclipse?
Super cool indeed.
The last few seconds is how I tell apart the original image and astigmatism 😅
"light bouncing incorrectly" these lenses break the rules of physics and we just shrug that off
"unintendedly" would have been a more appropriate word than "incorrectly".
Awesome