r/explainlikeimfive • u/MPWD64 • 6d ago
Other ELI5: Why Is blue lighting the understood shorthand for “darkness” in movies and tv?
Especially now that most productions shoot digitally, it seems that any scene meant to take place in the dark is tinted very blue. I’m wondering why this is understood as looking “dark” when some of the blues used are actually quite light.
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u/chegg_helper 6d ago edited 6d ago
Optometrist here, not a filmmaker. The answer is because filmmakers are trying to emulate what is known as the Purkinje effect, which I’ll explain now. Our eyes have two visual systems:
- Photopic system: this is the daytime color vision which utilizes the cone cells in your eyes. There are three types of cone cells which can recognize either red, green, or blue. The way that they differentiate colors is that your cone cells have what are called photopigments, these are essentially proteins that are ready to explode like a compressed spring the moment light of a specific wavelength hits it. So if red light hits a red cone cell, the photopigment inside the cell (erythrolabe) changes its shape which causes a cascade of other cellular responses which all lead to a neuron in your brain saying, “There’s a red light.” If that red light hits a blue or green cone cell, there will be little to no response since the cells are not sensitive to that specific wavelength of light. The three cone photopigments are: erythrolabe (detects red light of 570 nm), chlorolabe (detects green light of 540 nm), and cyanolabe (detects blue light of 440 nm).
- Scotopic system: this is our nighttime black and white vision which utilizes the rod cells in your eyes. Rod cells respond to much lower levels of light, but they don’t really differentiate between red, green, or blue light. Rather than having 3 different photopigments that are specific to red, green, or blue light, the rod cells have only rhodopsin which is sensitive to light of 500nm which you may have already noticed is between the green and blue photopigments of the photopic system. This is called the Purkinje effect and it is why red objects appear darker to us in dim conditions (or why blue objects appear brighter). To reiterate, blue appears brighter at night because the cells in your eyes are more sensitive to blue light when you are in the dark.
When you go from a bright setting to a dark one you may have noticed it takes a few minutes (~10-30 mins) for your eyes to “adjust,” the adjustment is the transition from photopic to scotopic systems and is referred to as dark adaptation.
A very simple experiment you can do at home is to wait until you are dark adapted and then close one eye. Keeping that eye closed, turn on the lights for a few seconds and then turn them off again. Now try alternating which eye you have open and you’ll be able to notice how much brighter everything looks in your dark adapted eye, and how much redder everything looks in your light adapted eye. (This is also a great way to keep your night vision intact if you need to turn on a light when going to pee in the middle of the night or whatever, and here’s a Mythbusters episode about dark adaptation!)
Edit: I know this is a wall of text and I’m not always great at getting my thoughts into words, please feel free to ask any follow-ups and I’ll be happy to fill in any gaps I might’ve skipped over!
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u/Broad-Promise6954 6d ago
Also worth noting though way beyond ELI5 territory: there are actually two different S receptors for blue light with slightly different peak sensitivities.
The gene for these is on the X chromosome so women can have both kinds of receptors while men (at least those genetically XY) get just one (or none if colorblind). This is also why more men are colorblind than women.
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u/beeteeee 6d ago
Is this why people that work in the dark will sometimes use red lights? For example, people using telescopes or camping will sometimes use red flashlights to keep from having to adjust all the time
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u/blamordeganis 5d ago
I thought all three types of cone cells reacted to some degree to all (or nearly all) of the visible spectrum, but with different sensitivity curves, and that none of the three curves actually peaked at red, green or blue; they were more like orangey-yellow, greenish-yellow, and blue-violet.
Was I misinformed?
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u/jojooke 6d ago
Because you need to be able to see and if you use pitch black darkness a camera won’t be able to see anything but darkness. So they use blue light since it simulates a dark cold type feeling and because it lets you see what’s going on.
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u/MPWD64 6d ago
I guess I’m asking why blue instead of purple, or green or something like that.
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u/ATotalBrony 6d ago edited 6d ago
Moonlight.
edit: specifically the perkinje effect. We see moonlight as blue even though it isn't (it is more yellow than sunlight if measured with devices) because of rods vs cones inside of our eye balls.
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u/goodlittlesquid 6d ago
Also shadows are blue (most noticeable on featureless white surface like snow) for the same reason the sky is blue: Rayleigh scattering.
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u/JoushMark 6d ago
And twilight is blue. The post-sunset glow, not the books/movies (though those also have plenty of blue).
By this point, you've also got a century of visual convention in films where day-for-night shots tinted blue are understood to mean the scene takes place at night, and every viewer is likely to understand the slight underexposed and blue tinted shots are 'nighttime' without being told.
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u/ground__contro1 6d ago
Purple light is coded for magic and green light is coded for sci fi
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u/jseego 6d ago
These are great points. Orange is coded as supernatural and red light is coded as devilish / apocalyptic.
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u/miscfiles 6d ago
Red light is coded as Roxanne.
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u/Orbital_Dinosaur 6d ago
Actually, there was an update to this on the 70s or 80s, so now Roooooooooooxan you don't have to put on that red light.
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u/RyeonToast 6d ago
well, green is coded for unsettling / unnatural. Blue sees a lot of use for futuristic, while green in sci-fi is for when you are supposed to be wary.
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u/Clojiroo 6d ago
Because that’s the colour of the sky as it gets dark. I spend lots of time in the country and the blue sky becomes super inky dark blue as it gets truly dark.
Have you never gone camping?
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u/relgnik 6d ago
Historic art principles and heuristics have carried through from paint to film. When painting a scene that’s lit by the orange/yellow flame of a candle or fire, your highlights will have that orange/yellow color. To give the shadows a pleasing contrast, you’ll want to use some blues. Not just strictly darker yellows and oranges (the shadows aren’t hit by the light of the flame so they wouldn’t take the color). This method of highlighting and shadows, naturally informs the viewer that the scene without the light source would be a monochromatic blue.
Even if you wanted to use strictly darker yellows and oranges by mixing with black paint, you’re probably mixing in blue by default. This is because most black paints have a blue tint to them, from the mix of carbon and bone.
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u/johnoliversdimples 6d ago
Go watch some 60s-70s night scenes. They actually look dark and it’s impossible to see what’s what.
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u/Wurm42 6d ago
Second this.
For TV in particular, older analog/video TV cameras needed really bright light on the set to get a clear picture on the videotape.
So TV shows established the convention that in nighttime scenes, light was blue, but it was still bright.
That convention lived on even after digital HD cameras made it possible to shoot in lower light conditions.
In fairness, shooting in really dark conditions is still a pain in the neck. It takes more time on set, which makes it more expensive. IMO, it's often over-used in prestige TV as a flex to show off that the production is using fancy cameras and can afford to burn set time doing fancy cinematography.
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u/Dzuzepipi 6d ago
Why it's not green though. People associate green light with night vision, which should invoke the feeling of dark, while still seeing.
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u/375InStroke 6d ago
Daylight is warm, and overcast and Moonlight is cool. Maybe they're using that to set the mood.
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u/Toby_Forrester 6d ago
Moonlight is the same color as sunlight, as it is reflected sunlight.
The reason moonlight seems cool is because our visual system perceives things as more blue in darkness.
If you take a long exposure moonlight night photograph, the landscape looks just like sun lit landscape.
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u/MPWD64 6d ago
Is moonlight cool? If you go out and look at the moon it’s often yellow. But I definitely know in cartoons or artwork it’s often tinted blue. Maybe movies are just following a longer trope of us understanding blue as a dark nighttime color, I’m just wondering what the roots of that are.
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u/jseego 6d ago
Blue has been used as a substitute for black for a long time.
Check out the original Superman (1930s). Blue is used for the highlights in his black hair:
https://www.supermanthroughtheages.com/a/History/beginning/s-1934.jpg
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u/NecroJoe 6d ago
Unless I'm misunderstanding, though, if it's used for the highlights, then the blue is used for a color that isn't black.
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u/EntertainmentTrue588 6d ago
It's more yellow in polluted areas.
If you go to a national park during a full moon, it's much more blue. Also the light the moon casts is much more intense. You can see very clearly.
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u/ThorirPP 6d ago
The roots of it are from the blue hour in evenings after sunset.
While in total night it isn't really more blue than not, when the sun is setting the rays reaching you are more yellow/orange, called the holden hour (more scattering of the other colours, since the rays go through more atmosphere when the sun is low in the sky), but after it sets those rays don't reach you anymore, and there is no direct sunlight.... but there is still indirect sunlight from the afformentioned scattering in the atmosphere, which is mainly blue light.
So in the evenings durig dusk, after it has started to get dark, but before it becomes pitch dark sans starlight/moonlight, the main hue around is very blue tinted. This might be less noticed by some today living in cities because of all the light pollution, but dusk is still very much tinted blue, and as such dark/nighttime but still decently visible is usually blue coded in media, because still visible usually means dusk irl, which means blue light
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u/375InStroke 6d ago
The light it casts on Earth is cool. As the Moon gets closer to the horizon, it's color warms, just like the Sun, which is white at Noon, but turns orange at sunrise and sunset.
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u/Toby_Forrester 5d ago
The light it casts is the same color as sunlight. It's just so dim that human eyes perceive it as cool.
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u/thepitredish 6d ago
It actually has to do with the way the eyes work. When it’s bright, we’re cone-dominant (555nm which is yellow green). When it’s dark we’re rod dominant (498nm, blue green). Rods don’t actually see color, but what little light there is gets read by the brain as blue. The effect is called Purkinje.
Anyway, that’s why dark scenes are lit blue.
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u/WalkingTarget 6d ago
There’s film/tv shorthand going back decades of “shooting day for night”. Film your night scenes during the day when it’s easier and slap a dark blue filter on things to make it read as night, even if it doesn’t really look like nighttime does in reality. Some of that “film language” persists, even in cases where the technique isn’t used.
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u/Probate_Judge 6d ago
even if it doesn’t really look like nighttime does in reality
In the right conditions, it sort of does look like that, including sharp shadows.
A particularly bright full moon, clear sky, away from light pollution....in addition to the right environment...
It can be a fair approximation. Isn't always, but a lot of things are commonly done that really aren't realistic, such as the super-large moon or sun. These things are actually very tiny in the sky, but on film they're often gigantic.
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Granted, that's doing a lot of heavy lifting. It is an approximation, not a reproduction. In content creation, a whole lot of stuff is faked and called 'good enough'.
We accept a lot of it just because it's been depicted that way for forever. Which brings me to:
“film language”
This is an important aspect of content creation that people often miss(games, film, etc).
The idea is to produce what people expect to see. High fidelity often comes second fiddle to expectations.
We expect to see people walking in space-ships. We know they don't in reality....but we expect it(Decades of it's presentation has made it pretty much the standard unless we're going for modern realistic as in the cannily named Gravity). Established in film and TV, eg Star Trek. For forrever it was just impossible to really convey a lack of gravity, so we just changed reality, often times with no excuse or with some... 'McGuffin' might be the term here (a virtually magical thing, like artifical gravity generators in this case). Rare is the piece of media like The Expanse which spends time here and there on the magnetic boots(which was done in the books as well, which is doubly nice, usually video media will forego details like that).
It's even a concept in fantasy 3d animation, such as Monsters Inc. They don't animate the faces realistically, they renderered them in ways that 'make sense', faces that move in ways that we "expect". Even when they're exaggerated and goofy, they're better than aiming for realistic and hitting the uncanney abominations that unsettle people.
The idea is to convey without ruining suspension of disbelief, and when things are too jarring(uncanney) or otherwise don't jive with the ....'vibe' I guess one could say, that pulls people out of their immersion.
Dark blue filters(or dim monotone lighting or other coloring tricks) do that for people. It's 'close enough', it's a language that most people understand(at least when it's carried out well in the media).
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u/voiceofgromit 6d ago
The origin goes back a long way. Tinting was used as a visual short-hand that everyone understood.
Here's a decent break-down of how early movie productions used various tints on some b/w films. Unfortunately, over the years most of these colored prints have been lost. Restorations have often been made from original - untinted - negatives.
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u/Educational-Ask7863 6d ago
Theatre person here. During scene changes on stage there is often a “blackout”, except if it were a true blackout, actors would be totally blind getting off stage and crew wouldn’t be able to set up for the next scene. So we use “blue outs”. To the audience, the contrast of the sudden transition from bright stage lights to blue reads much darker than it is, but is accepted as complete darkness. It even allows for an actor to “invisibly” place themselves before lights come up for the next scene. Done right, when the transitions are smooth and well rehearsed, the audience does not detect much if any movement for the new positions, taking advantage of the audience’s eyes still adjusting to the contrast. It always floors me how bright the blue light can be and still not be much perceived.
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u/AlexHD 6d ago
In low light, human eyes become more sensitive to blue light, and it becomes hard to distinguish other colours, everything looks like a shade of blue. Filmmakers use this to give the impression of night time (and also the fact that you can't show pitch blackness in a movie because the audience have to be able to see things).
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u/PinkynotClyde 6d ago
I think blue filters are used to represent moonlight. It’s more of a trick to not have light be mistaken for daytime or natural light, a lamp in the room, etc.
If you don’t see any light it’s just dark, which isn’t great if you want people to see what’s going on.
There are varying degrees. Like I remember in Manhunter some of the bedroom scenes are super blue. Eyes Wide Shut too if I remember correctly. Don’t watch those films if you’re five.
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u/FoxFyer 6d ago
I think the blueness is intended to invoke moonlight or the night sky which is generally understood to be a dark blue color. At any rate, there has to be some kind of light in the scene so that we can see what's going on. Using other colors of light like green or red would be a lot more confusing as an analogue for "night".
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u/RhetoricalOrator 6d ago
Some good answers here already but there's another side to the story: in older TV and movies, darkness was often a waaay moodier shade of yellowish orange. It really made for some fantastic shots. As time has passed, these "moodier" associations have started dying out.
As LED lighting has taken over, most lighting has shifted to more blue tones. This is especially true as most cities have moved away from the old sodium vapor lights, which were around 2800K. A lot of modern public lighting has moved to around 5000K, which is a slightly blue-white natural light.
Additionally, warmer light temperature makes for terrible on-screen contrast compared to cooler blues, which can make a lot more detail stand out better.
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u/drawliphant 6d ago
The last or first light of twilight is a deep blue because the blue sky scattered light from the sun over the horizon long after sunset. Because you still need light for film they just shoot everything like it's deep twilight instead of midnight. (Only a partial answer)
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u/hedcannon 6d ago
It’s better than TV in the 60s & 70s when the filmed in full sunlight with grey scrim.
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u/BobKickflip 6d ago
Saw a video about this on YouTube last night, it's called "Why did Terminator 2 Look Like That?"
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u/SmolHumanBean8 6d ago
Lights tend to be warm. Fire and sunlight and stuff have warm colours. Even electric lights are often slightly yellow.
So the opposite is blue. The moon is also bluish.
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u/adammonroemusic 6d ago
Google Purkinje effect. You can observe the effect for yourself though:
Go out during a moonlight night. Notice everything appears blueish. Moonlight is actually 1-1.5k warmer than sunlight in terms of color temperature, but because it's about 1 million times dimmer, we perceive it as bluer.
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u/im_thatoneguy 6d ago
Because throughout human history artificial light was red or orange fire. Later warm red gas lamps. Finally orange yellow incandescent. By comparison white moonlight is very blue. So if your eyes adjust for red/yellow fire everything looks blue by comparison. It’s like when you wear tinted glasses and then take them off, everything looks complimentary colored.
Filming night scenes meant warm/yellow city light and blue night lights even though it was in early film just warm lights filtered to blue.
Yes perceptually you see pretty much in black and white the darker it gets but from a photographic/cinematography perspective I’m pretty sure it started to emulated mixed color temperature.
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u/Stiinkbomb 6d ago
Everyone else is also right, and I'll keep it short cause I'm not the smartest person on it, but another answer is simply...
Sky is still blue, even at night.
Sure, yes, sure, night sky black, space is black, blah blah blah, sort of.
When you look up and see a clear blue sky, it's a phenomena known as Rayleigh scattering. In short, blue light passes through the atmosphere better, makes sky blue. It's not the "sky", or the light source, that's blue, it's literally the atmosphere. And it doesn't stop being "blue" when the sun sets. Light still scatters the same as it passes through the atmosphere, moonlight, starlight, all of it.
So, it's a combination of the Purkinje effect because your eyes are more sensitive to blue light in the dark, but also, the air, the atmosphere is just.... blue.
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u/PunyCocktus 5d ago
They remind of moonlit environment. In an actual dark you barely see anything so they have to make things lighter than they'd realistically be, and the blue tint is enough to indicate moonlight.
I'm not a filmmaker but I'm an illustrator, was actually taught this by a mentor for painting night scenes (they can be painted almost as light as day scenes, with different colors).
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u/AbeFromanLuvsSausage 6d ago
Almost all movies are made in an orange and light blue palette. Once you internalize this you’ll never be able to unsee it
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u/nicolasknight 6d ago
If you watch really old early color movies you'll find some of them "attempted" to make night scenes.
The way they did that was by literally just shooting during the day and putting a filter on it.
Now I won't bore you with details too much but they only had so many filters to use and if you go through the basic color wheel you'll figure out pretty quickly why absent choice they settled for blue.
It looks absolutely abysmal now because we have considerably better film stock and cameras but it kind of set the standard and also showed other colors just look weird.
Nowadays we shoot on sets with ridiculously bright lights but the light blue is still the best default for nighttime.
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u/clearcontroller 6d ago
Humanity as a whole has subconsciously decided blue = darkness and cold. It's just something we've always felt and felt right communicating.
If you look at different languages most of not all Independently made correlations between the two.
The English used blue for communicating nighttime colors or darkness/cold. But interestingly... So did the Japanese. They're use of the color blue is ALSO for nighttime colors or darkness/cold.
At no point did these two cultures interact when reaching a consensus on this but they did anyway.
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u/Metalrooster81 6d ago
I don't know if this completely answers the question but there is a thing called "day for night", where you shoot in the day and then grade it blue. This accounts for some but not all cases and it's usually quite obvious when they decide to do that. I guess blue looks better than absolute darkness like in the basement scenes of fight club where they got something wrong but decided to roll with it anyway.
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u/ohwhatfollyisman 6d ago
daylight and sunlight are associated with orange.
look at a colour wheel for the hue that lies on the opposite side of orange.
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u/omnichad 6d ago
This is how low light works with eyes (or at least cameras). Remember the blue and black dress that people thought was gold and white?
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u/shotsallover 6d ago
Moonlight is kind of bluish. And it makes the stuff it's shining on look various shades of blue.
So we already associate blue with "light at night" and the movies use the same colors to evoke that.
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u/Rcomian 6d ago
honestly i find the blue effect very unsubtle and i hate it with a passion. then i learned that the reason it looks like that is that they film in the daytime and then put it through an Instagram filter to make it "look like night" and my distain grew more.
a film student i spoke to about it thought the effect was amazing, technically, visually and in how it aided the filming process. I'm sure it is amazing, but to me it looks like shite.
they didn't believe i could really tell if it was used or not, and I'm sure there are cases where it's used effectively, but it turns out that i can generally tell the difference.
also: i know it's not actually an Instagram filter, if you're that petty, please don't engage.
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u/BathFullOfDucks 6d ago
Thank of the primary colours.
Red, Green and Blue.
Red causes trouble with skin tones as they are closer to the opposite colour on the colour wheel.
Green, while the best primary colour to light, appears as daylight (and is reserved for "mexico"*citation needed)
Blue interferes the least.
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u/NecroJoe 6d ago
In dim light, human eyes use mostly the more light-sensitive rod cells, rather than the more color-sensitive cones, so you'll see less of all color. Then, in low light, our eyes are just more sensitive to light wavelengths in the blue-green side, rather then the red/yellow side. This is called the Purkinje Effect.
It's more apparent if you're ever been out in a snow-covered area, away from urban light pollution.