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LuxeSci Show Notes: S2E1: How Do We See Color?

Welcome back to Luxesci, the podcast to reignite your wonder by exploring the science of luxury items.  We’ve been away for a bit settling into our new life in Greece.  We’ve also been thinking up Season 2 of LuxeSci.  Season 1 was a bit of a mash-up starting with a solo host and seemingly random topics and evolving into this co-hosting relationship and focusing on the materials that make-up fine jewelry.  Now, for Season 2, we’ve been inspired by all the amazing ancient and modern art that we’ve seen while we’ve been exploring Athens so we’re going to spend this season discovering the science behind visual arts.


But first, we should probably re-introduce ourselves since we’re starting a new season. I’m Dr. Lex.  I have a PhD in Microbiology and Immunology and a MS in Public Health Microbiology from The George Washington University.  I’ve worked for US government health agencies, small and large non-profit and philanthropic organizations and private drug development companies.  This podcast was born out of my experience running a data management team that was involved in HIV and COVID clinical trials.  COVID highlighted for me how many people felt scared or intimidated to engage with science so I decided to start talking about the science behind the things I like and since I’ve always been accused of having fancy taste, we started there.


I’m Dr. Dimos.  I have a PhD in Power Electronics Reliability and Material Science and a MS in Electrical Engineering from Virginia Tech. I have worked for large companies, the US military and had my own solar power inverter company.  I started as the audio engineer and then was interviewed for our episode on space travel and became a more front-and-center part of the podcast.


So visual arts?  Dimos - what do you think of when you think of visual arts?


Color Theory

  • One of the first things i want to know about something new we’re looking into is to know how to talk about the topic.  Most occupations, and scientists especially, have their own language related to their field.  It can be difficult even for people who’ve spent their life in science to decipher the language of another scientific field. 

  • When i was first reading up on this topic, i came across the mention of color theory and there seemed to be quite a few different color theories and I thought, oh boy, this is going to be difficult to wrap my head around.  Are they competing theories? Will I have to know all of them?  

  • Fortunately for me (and you) color theory is not only interesting but there are some great resources out there to help us all be conversant in the different theories

  • I’m not going to cover them all - here are the ones i thought would be most pertinent to our conversation

  • Additive and subtractive color theories are mostly are the color theories found in art since they deal with mixing light (additive) and mixing pigment (subtractive).

  • Additive color theory - describes how light creates color and is what your camera, telephone, television and computer used to create color. This model starts with black and red, green and blue light is added to produce the visible spectrum of color. For this model, adding more color equals lighter until you get to white.

  • This is basis of the color theory we all learned as kids when we said that black is the absence of color and white is presence of all the colors.

  • Subtractive theory - instead of using light, this model uses pigment to create color (and thus is for printing, silk-screening and painting.  The color used in this color theory are cyan, yellow, magenta and black.  Instead of starting with black, as with additive color theory, this model starts with white paper.  Pigment is added to create the color and the color gets darker with the addition of more hues.  Theoretically, equal parts of all the colors should result with black. But as we all know from mixing all our paints when were were little, the result is usually brown.  Which is why we have black pigments.

  • There are other theories of color that are more linked to how we see color, such as trichromatic color theory, which states that we have red, blue and green cones and every color is a combination of those and the opponent process theory, which is were perception of color is mediated by color channels.  Both of these are accurate but describe how color is perceived on different parts of the brain.

  • Trichromatic - how cone receptors detect different wavelengths in light

  • Opponent processes theory - how cone receptors connect to the nerve cells and this determines how we perceive color

  • The interpretation of the color

  • Language of color

  • Since i’m currently trying to learn a new language (Greek), I thought it would be interesting to look at the research around how we talk about color in different languages

  • I found a paper from 2017 PNAS (Protocols of National Academy of Science) by Gibson et al

  • They focused on the color categories of Warm and Cool - which they theorized are not universal categories across languages

  • To test this - the authors adopted different methods of interpreting the instructions of the World Color Survey

  • Survey that originated in the 1970s to investigate the findings of Berlin and Kay that there were universal ways of naming colors across languages

  • 24 participants of 110 languages

  • Consists of chips of colors with various ways of using them to elicit terms for color - such as saying ‘blue’ and having the participant point out all the chips that would identify as blue

  • Also questioning designed to find the smallest number of simple words with which the participant could name any color.

  • The authors used three groups (and not the 110 languages), an indigenous group from Bolivia (Tsimane), English speakers in the US and Bolivian SPanish speakers

  • Used an information theory to develop a way to rank the colors for their relative communication efficiency within a language

  • Results

  • Efficient-communication hypothesis

  • Color categories reflect a tradeoff between informativeness of the terms and their number

  • Reconciliation of the views that color categories arise from universal underlying principles and that color categories arise from the culture

  • Cultures do show common naming practices for colors

  • However, warm colors are more precisely communicated than cool colors. 

  • Link between warm colors and behaviorally relevant items - salient objects - in the environment

  • Analyzed colors of objects in 20,000 photographs and found that most of the objects were warm colors and the backgrounds were cool colors

  • Thought it was really cool to learn that there are similarities to how we name colors (especially since it feels like there are no similarities between the Greek and English colors)

  • Really liked the observation of warm colors being more objectives and cool colors being more the background and maybe that’s why we have more synergy on naming the warm color category

Physics:

When you research color you might come across statements like, The spectrum of color ranges from dark red at 700 nm to violet at 400 nm. This might be useful in some ways if you think of it like the way we hear things. We know that frequency of sound is perceived across a frequency spectrum and that the noise created in an instrument is not transmitted directly but instead carried by air molecules to our ears. Photons carry energy from light sources and the objects they strike in a similar manner. Just like sound waves, photons also carry energy and interact not only with the objects they strike but also with our light receptors in our eyes. The one difference is photons are their own vehicles of energy, sound waves are ripples through a material like air but both contain vibrations corresponding to color or a note. An important parallel is the existence of the doppler effect, the change in perceived frequency when a sound wave is coming from a source towards the ear. In astronomy, where light producing objects can also move quickly, this behavior is quite real and gives us a measurement of the speed of objects around us in the universe.


As an example of color frequency, take a perception of fruit color, like an orange, all wavelengths of the visible spectrum are absorbed except for the specific wavelengths that we process as orange, which are reflected back to our eyes. What is absorbed depends upon the arrangement of electrons in the atoms on the surface of the material. We see an orange as orange because the electrons in the atoms of the orange peel absorb all other wavelengths of the visible light except orange, which are reflected back to the eye. Once the orange wavelengths reach the eye, the cones that correspond to that wavelength are then stimulated to a certain degree and then that information is passed to the optic nerve to the brain to be processed by the visual cortex into the “color” orange that we perceive. Not a lot of photons are needed to process images in the retina but certainly more are needed for color than are needed for simple light vs. dark perception.

How does a cone process a photon?

Cones in the retina are the color processing part of our eyes. They combine photo-receptor proteins into photo-receptor cells that can change “membrane potential” and transmit this to bipolar cells which convert this “membrane potential” to a signal that can be processed by a ganglion cell in the optic nerve.

Humans normally have three types of cones, usually designated L, M and S for long, medium and short wavelengths respectively. The first responds the most to light of the longer red wavelengths, peaking at about 560 nm. The majority of the human cones are of the long type. The second most common type responds the most to light of yellow to green medium-wavelength, peaking at 530 nm. M cones make up about a third of cones in the human eye. The third type responds the most to blue short-wavelength light, peaking at 420 nm and making up only around 2% of the cones in the human retina. 


Cones also tend to possess a significantly elevated visual acuity because each cone cell has a lone connection to the optic nerve, therefore, the cones have an easier time telling that two stimuli are isolated.


So.. when a photon enters the eye and falls on a cell of a matched wavelength, a series of reactions happen in response to the photon. A photoreceptor protein called transducin is the key element used by vertebrates which is the beginning of a chemical reaction used to “amplify” the photon’s arrival. These proteins called Retinal (also known as retinaldehyde) is a polyene chromophore that in simple organisms can convert light to cellular energy not unlike a solar cell. The reception of light results in a change in shape of the protein as a reflex due to the chemical changes that are responding to that particular photon. This results in a small change to the shape of the disk cell containing the proteins. Enzymes are created in response to the photon, and a catalyst that responds to the new enzymes by cutting off the flow of sodium through the cell membrane for a short time. The result of this is that the cell wall creates a voltage relative to other cells in the vicinity and allows the bipolar cell to register that difference in voltage. This bipolar cell takes the measurement and transfers it as a stimulus to the ganglion cell that interfaces to the optic nerve.


Glossary:

  • Additive color theory - theory that explains how light creates color but adding red, blue and green and ends in white

  • Subtractive color theory - for mixing pigments and starts with white canvas and then adds color to get to black

  • Cone receptor

  • Wavelength


Fun Party Facts

  • Which category of color is more conserved across cultures in terms of naming? 

  • Which color theory starts with white and ends with black the more color is added?


Thank you again for listening to this season premiere of LuxeSci.  As always, many thanks to my cohost and audio engineer, Dimos.  OUr theme music is Harlequin Mood by Birdie.


You can follow all over social media at LuxeScipod.  Definitely give our Youtube channel a follow since we’ve been posting weekly cocktails and science discussions (Science Sips), some videos from around Greece and our LuxeSci Field trips


Your assignment for the next two weeks: leave us a review on Spotify, Apple Podcast, Youtube or wherever you listen to your podcasts.



Music: Harlequin Mood by Burdy


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