The reason we cannot detect UV or IR is now easier to address: these frequencies are not detected by any of the cone cells. So the combination is basically $(S,M,L)= (0,0,0)$ The number of distinct colours in the brain’s vocabulary (considering perfectly functioning receptors and other mathematical idealizations necessary) is therefore the number of ways of partitioning the number of colour receptors we have into three subsets. If you place the subject in a perfectly dark room and illuminate the room with UV rays, the brain gets a $(0,0,0)$ signal, consults its dictionary, and reads it as ‘black’ (assuming the illuminating radiation isn’t one that burns out the eyes, in which we could probably tell in retrospect that it wasn’t black).
How can I make sense of the way (screen) colors are generated? [duplicate]
OK here is some common knowledge I have from the net: a computer screen has 3 constituent colors of red, green, blue. To make all spectra of stuffs it just combines them. We also know that red is about 650nm, blue 470 and violet 425. In real life, mixing yellow and blue creates green, a color in-between. So how the hell can computers combine red & blue to give violet? In my understanding, (650+470)/2=425?? Using that absurd principle, then surely it’s possible to create IR & UV light by mixing RGB on a computer screen? Bonus question: to make things more perplexing, let’s add biology in for a bit. Our eyes have 3 types of cones with maximum responsivity near computer’s RGB values. When a natural light strikes our eyes – say from a pure 425nm violet flower – according to a Wikipedia picture I can say that the S-cones are highly activated while M & L are barely on. See, that’s very different from the combination of red & blue excitation that screens give us. So. should we conclude that computer colors are “fake”?
- visible-light
- electromagnetic-radiation
- computer
Cite
Follow
longtry
asked Mar 20, 2020 at 3:07
longtry longtry
181 5 5 bronze badges
$endgroup$
$begingroup$ The post – What is Gray, from a physics POV? – has more on it. physics.stackexchange.com/q/339130/37364 $endgroup$
Mar 20, 2020 at 4:22
Mar 20, 2020 at 7:01
$begingroup$ mmesser314: hmm, actually I do understand gray. PM2Ring: well, while I can grasp some of the info there, those Wiki articles are pretty hard to understand. For example, I still don’t get what x & y in the CIE graph stand for. sammygerbil: that answer adds a very interesting tidbit that I didn’t even know and don’t intend to ask in this question 🙂 $endgroup$
Mar 21, 2020 at 3:36
2 Answers 2
Sorted by: Reset to default
$begingroup$
The computer screen RGB color mapping protocol takes advantage of metamerism, which is the physiological optics effect wherein stimulation of the different color receptors in the human retina produces a full range of perceived colors in the brain– even though the retina is being presented with a combination of ONLY red, green, and blue wavelengths.
We can therefore conclude that the computer screen is exploiting metamerism to trick our brains into believing the screen generates a full-color spectrum when it actually does not.
Cite
Follow
answered Mar 20, 2020 at 3:18
niels nielsen niels nielsen
89.8k 16 16 gold badges 127 127 silver badges 232 232 bronze badges
$endgroup$
$begingroup$ Then in theory, it’s possible to have only 2 supercones and being able to perceive all colors ranging from radio to gamma, right? Those 2 types of cones just need to have 2 very, very long excitation ranges, which overlap for an also very long range. $endgroup$
Mar 21, 2020 at 3:48
$begingroup$ suggest you search on “physiologic optics” for more info. -NN $endgroup$
Mar 21, 2020 at 4:57
$begingroup$
As the other answer already tells you, computer colours are indeed fake, they rely on the way human beings perceive colour. I want to answer your question about generating UV and IR frequencies, but first, a detour. Let us say that the circle of minimum area that a human eye can discern has area A. For two such circles adjacently placed, the human eye can distinguish their colours. On the other hand, if we place smaller circles of two different colours $C_1$ and $C_2$ adjacent to each other, the eye discerns one blob of colour $(C_1+C_2)/2$ , pretty much like your “absurd principle”, except that we do not literally add wavelengths in our brain. Instead, the eye has three specific, independent colour receptors, and any other colour is indexed in the brain by what combination of these three generators is involved in it. The point is that the brain is not measuring wavelengths, it is measuring number of cone cells of each type excited by the incoming light, and reading off the colour from its inbuilt dictionary, say $bigg(frac S+frac M+frac Lbigg)=text$ or some similar algorithm.
The reason we cannot detect UV or IR is now easier to address: these frequencies are not detected by any of the cone cells. So the combination is basically $(S,M,L)= (0,0,0)$ The number of distinct colours in the brain’s vocabulary (considering perfectly functioning receptors and other mathematical idealizations necessary) is therefore the number of ways of partitioning the number of colour receptors we have into three subsets. If you place the subject in a perfectly dark room and illuminate the room with UV rays, the brain gets a $(0,0,0)$ signal, consults its dictionary, and reads it as ‘black’ (assuming the illuminating radiation isn’t one that burns out the eyes, in which we could probably tell in retrospect that it wasn’t black).
Cite
Follow
answered Mar 20, 2020 at 3:48
NewUser NewUser
669 4 4 silver badges 9 9 bronze badges
$endgroup$
$begingroup$ I think violet is like (S,M,L) = (.9, .2, .1), but I get your point. Do you have any links for the C1, C2 experiment? $endgroup$
Mar 21, 2020 at 3:39
$begingroup$ cool, i just put in three random numbers. do you have a reference for a standard scale used in biology? $endgroup$
Mar 21, 2020 at 3:43
$begingroup$ Er, no. I don’t even have any idea about biology having any standard scale about this $endgroup$
Mar 21, 2020 at 3:46
$begingroup$ the $C_1,C_2$ averaging i talked about were mostly an attempt to derive a very simple model for generating all colours from three inputs. most biology resources say the brain “integrates” the input from the three types of cone cells to decide the colour, but they do not describe an equation for it. i wouldn’t guarantee that the actual algorithm is an unweighted average, so my answer is more of a model than “the” model used by the brain. $endgroup$
When a white light beam is made to fall on a hollow prism filled with water, it breaks into seven constituent colours. Which of the following colours suffers the maximum angle of deviation?
EXPLANATION:
- The deviation is maximum for violet color and minimum for the red color of light.
- According to the question, blue comes after the violet hence, it deviates the most.
- An optical prism is a transparent optical substance with flat, polished surfaces that refract light.
- The different colors that make up white light become separated.
- This happens because each color has a particular wavelength and each wavelength bends at a different angle.
- When a ray of white light is passed through a prism gets split into its constituent colors. This phenomenon is called the dispersion of light.
Share on Whatsapp
Latest UPSC CAPF AC Updates
Last updated on Sep 12, 2023
UPSC CAPF AC Written test Result has been released! the exam was held on 6th August 2023. the qualified candidates will now appear for UPSC CAPF AC PET. The UPSC CAPF AC Notification was released. A total of 322 vacancies have been announced. Candidates had applied online till 16th May 2023. The selection process comprises of a Written Exam, Physical Test, and Interview/Personality Test. The finally appointed candidates will get a salary in the range of Rs. 56100 to Rs. 177500. Candidates must attempt the UPSC CAPF AC Mock Tests for a better understanding of the syllabus. The UPSC CAPF AC Previous Year Papers are a great source of revision of the entire syllabus.
Stay updated with General Science questions & answers with Testbook. Know more about Physics and ace the concept of Wave and Light Wave
Understanding the Meaning of Color Within Design
Color is the perceivable characteristic of light; light is energy, so color is a form of energy. In 1666 Sir Isaac Newton discovered that sunlight is a mixture of colors by noticing that when a ray of light passes through a prism, it is dispersed into its seven constituent colors: red, orange, yellow, green, blue, indigo and violet.
We see different colors because some objects reflect/absorb specific wavelengths. Human eyes perceive these wavelengths as colors.
Understanding Color
In web design colors are very subjective; take black for example, for some it is the color of elegance, and it sometimes gives the idea of prosperity (you may immediately imagine a black and elegant limousine), but for others it can be a reminder of something unpleasant (death, hopelessness, evil, mourning).
You can’t use only a single color in your work even if it is a site, logo or a business card. It needs to be a combination of two or more colors to be effective. Unfortunately making a wise mixture poses a tough choice; the modern monitor displays can render more than 16 million (16,000,000) colors. Therefore it’s very easy to make a wrong choice.
To combat these situations, designers and in particular web designers, have an important and useful guide to color theory. This is a set of principles that help create harmonious color combinations.
Primary Colors
In traditional color theory, there are only three colors which can’t be formed by combining others, to be more specific there are only three colors from which all the rest are created. These colors are: red, yellow and blue – primary colors.
Secondary Colors
Mixing the primary colors we will get the secondary colors – green, orange and purple.
Tertiary Colors
Tertiary colors are combinations between primary and secondary colors (yellow-orange or marigold, red-orange or vermilion, red-purple or magenta, blue-purple or violet, blue-green or aquamarine and yellow-green or chartreuse).
Cool & Warm Colors
As in life, harmony consists of a well balanced arrangement of the parts. To establish some relationships between colors in color theory we distinguish two categories:
1.Warm Colors are the colors from red to yellow including brown, orange, pink. These colors evoke warmth because they remind us of things like the sun or fire. These tend to advance in space.
2. Cool Colors are from green to blue, but also include some shades of violet. Cool colors are better for backgrounds and will
give the impression of calm and reduce tension.
White, black and gray are considered to be neutral.
Useful Color Theory Terms
These terms are very useful in color theory too:
- Color Value measures lightness or darkness of a color.
- Saturation or intensity is the brightness or dullness of a color.
- Chroma is how pure a hue is in relation to gray.
- Shade: a hue produced by the addition of black.
- Tint: a hue produced by the addition of white.
We use different sets of primary colors, the widest used being:
- RGB color: this is based upon light. “RGB” stands for Red, Green and Blue (are the primary colors with green replacing yellow). Computer monitors and TV sets use RGB, but not used in printing.
- CMYK color: this is based upon pigments. “CYMK” stands for Cyan, Yellow, Magenta and Black (K stands for black).Using these four colors most of the others can be achieved. CMYK can produce less colors than RGB (yellow-greens sometimes doesn’t have the best quality).This system is used in printing.
- Pantone (PMS) Color: this is another system used in printing; PMS stands for Pantone Matching System and is a very large list of color mixtures made by the Pantone Corporation. Unfortunately they are very expensive.
- Hexachrome: more recently Pantone developed another system, based on the regular cyan, yellow, magenta, black and in addition Pantone Hexacrome Orange and Pantone Hexacrome Green. It will be used and it is used in printing, being a step further than PMS or CMYK.
The Meaning of Color
Have you ever asked yourself why Las Vegas is the city of red neon? This is because red makes people take riskier actions than blue, that calms down the spirit. Scientists demonstrated that colors have an impact on the human brain. Thus a human being exposed to a certain color can have different reactions, some are excitant, and others increase appetite or give the feeling of warmth or coolness.
Like we mentioned previously, colors are subjective and for each of us a color has an individual impact, but generally accepted meaning of these are as follows:
- black: mystery, elegance, death, evil, power, mourning.
- blue: sadness, calm, loyalty.
- green: abundance, nature, freshness.
- yellow: happiness, concentration, hope.
- red: passion, anger, danger, love.
- white: purity, cleanness, innocence.
- purple: royalty, luxury, wealth, sophistication.
- cream: elegance, purity.
- gray: conservative, formality.
But there are some specific interpretations in certain countries or regions:
- Black is the mark of high quality and trust in China.
- Blue in Iran has the meaning of immortality.
- Green means high-tech in Japan, luck in the Middle East, death in South America.
- Yellow is the color of mourning in Mexico and gives the feeling of strength in Saudi Arabia.
- Red has multiple meanings, from good luck in China, danger in Europe to mourning on the Ivory Coast and death in Turkey.
- White means mourning in Japan.
Is Color our Friend or Foe?
Colors can be a great friend within, but they can also be a very powerful and strange enemy. Strange…? Look at the pictures below, how many colors you see?
You will probably believe that there are four.
The correct answer is only three. Don’t forget that color is light, light is energy, so color is energy.
