Light On Color: Illuminate

Light On Color: Illuminate

In the last several Artissima blog posts we have taken a  journey through some of the aspects of color that many of us find challenging to truly understand, and wrap our minds around.

It has been fascinating to tackle the topics of metamerism, spectral reflectance, spectral power, the color rendering index, and color temperature.  I wanted to take a few moments, and summarize what I have learned, and hopefully what you have learned too!

As discussed,  color is a function of light. The color that we  see  is  reflected light waves.   “Visible light is made of seven wavelength groups.  When light hits objects, some of the wavelengths are absorbed and some are reflected, depending on the materials in the object. The reflected wavelengths are what we perceive as the object’s color.”

We recognize four types of Metamerism, the phenomenon of colors seeming  to match under one light source, yet appearing different under another/in a different environment.

Sample metamerism: when two color samples appear to match under a particular light source but do not match under a different light source.   Sample metamerism has to do with differences in each sample object’s spectral reflectance distribution, or its response to light, characterized by the wavelengths that it primarily reflects. It happens because of differences in the objects (or samples) themselves.

Illuminant metamerism:  occurs when the spectral reflectance distributions of the two color samples observed are identical, and are seen under different lights sources with differing spectral power distributions  (SPD, or output of a light source, characterized by its relative strength at each wavelength.  It happens because of the light sources (or illuminants) themselves.

Sample Metamerism occurs as a result of  differences in the reflectivity of the color samples themselves, and Illuminant Metamerism occurs as a result of differences in the output of the light source itself, under which we are viewing the color samples.

Observer metamerism: can occur because of differences in color vision  from one person to the next. The physical act of seeing, that which happens in our eyes and brains when we see an object in whatever light, can alter  our color perception. A common source of observer metamerism is color blindness,  but it occurs with the “normal-seeing”  as well.  What  may be a color match for one observer may not be for another.

Geometric metamerism: The angle, distance or light position from which identical colors are viewed may change the color that we see. The distance between a woman’s eyes is, on average, slightly less than a man’s.  This slightly different angle of stereoscopic viewpoint may be why men and women have been known to perceive colors differently!  Most of us have had the experience of  two samples appearing to match when viewed from one angle, but then not matching when viewed from another angle.

CRI, or The Color Rendering Index is an international measurement scale that measures or  describes how colors are rendered, IE “show up” to our eyes,  under an artificial source of light as compared to daylight. Daylight renders the widest variety of colors, as compared to artificial lighting, which depending on the nature of its light source, can render many or few colors.  The International Commission on Illumination (Abbreviated C.I.E. because of its French name, Commission internationale de l’éclairage)is recognized as the  international authority on light and color.  It defines  CRI/color rendering as the effect of an illuminant on the color appearance of objects by conscious or subconscious comparison with their color appearance under a reference illuminant.

in my own words, the color rendering index describes the  effect of a light source on how the color of an object appears to us.  It is the measurement of how much an object’s color appearance shifts when illuminated by an artificial (other than daylight)  light source compared to the color appearance of the same object when  illuminated by a “reference” light source (daylight), of comparable color temperature.

Color Temperature… refers to the actual color and type of  light emitted by a particular light source. High color temperatures, those over 5,000K (K = Kelvin) are termed cool colors  and are bluish white, while lower color temperatures (2,700–3,000 K) are called warm colors  and are yellowish white through red.  

Thus, color temperature refers to the actual color of light and  CRI refers to the ability of a light source to render color, in comparison to daylight.

The relationship of color temperature to CRI?

The color rendering index can be used as a basis of comparison between light sources only if they have the same color temperature; if they are the same degree Kelvin, and thus the light they emit is the same color.

CCT, or Correlated Color Temperature, also expressed in Kelvin, is a numerical description of a  light’s color appearance,  and describes whether a white light source appears more yellow/gold, or more blue.  CCT can be used as a means of correlating the color of an artificial light source with the color of daylight.

As artists, colorists, visual makers of any kind, and humans upon this earth…we will always come back to our response to color, how it is perceived or rendered through light, its effect on our interior and exterior environments, and upon our hearts, minds and souls, to say nothing of our work. Color, and thus light, are a frame of reference for our physical and emotional  experience as we move through our lives.

I hope these posts have shed some light on the color in your life….and that you walk in beauty…and illumination.

 

Color Temperature

Color Temperature

What is “Color Temperature“, and how does it relate to CRI, or the Color Rendering Index?

We know CRI to be an international measurement scale or rating of how accurately an artificial  light source renders, or shows the color of an object (often called its “color appearance” ) as compared to daylight, which is capable of depicting, rendering or showing the widest range of colors. Thus, CRI rates, describes or measures how the  colors of objects  appear (compared to daylight) under a specific light source…IE, in a given light.

Color temperature however refers to the actual color and type of  light emitted by a particular light source.  High color temperatures, those over 5,000K (K = Kelvin) are termed cool colors  and are bluish white, while lower color temperatures (2,700–3,000 K) are called warm colors  and are yellowish white through red.

Yes, counter-intuitively, the higher color temperature describes a cooler color, while a lower color temperature describes a warmer hue. When considering interior lighting,  color temperature can play a significant role in how we feel and function in a space.  A warmer light, which has a  lower color temperature, can  promote our relaxation, while a cooler  light with a higher color temperature may enhance or help to increase our concentration.

Thus, color temperature refers to the color of light, and CRI refers to the ability of a light source to render the color of objects in a manner comparable to the way daylight does/would.

Whew…what a mouthful!

The rub?  The color rendering index can be used as a basis of comparison between light sources only if they have the same color temperature. To compare light sources, or to compare an artificial light source to daylight, said artificial light source must have the same color temperature as the daylight to which it is being compared.  Remember, daylight renders, or makes visible, the widest range of colors…and there are yet many more colors in the light spectrum that we cannot see with our naked eyes.  We are not able to see the entire light (thus color) spectrum. Light values beneath the visible part of the spectrum are referred to as infrared, and above the spectrum as ultraviolet.

CCT, or Correlated Color Temperature  is expressed in Kelvin, and describes whether a white light source appears more yellow/gold, or more blue.  Thus, it  is  a numerical description of a  light’s color appearance.  It can be used as a means of correlating the color of an artificial light source with the color of daylight. “The correlated color temperature (CCT) is a specification of the color appearance of the light emitted by a lamp, relating its color to the color of light from a reference source when heated to a particular temperature, measured in degrees Kelvin (K).  —http://www.lrc.rpi.edu/education/learning/terminology/cct.asp

Here, we bring our discussion of Color Temperature, and its relationship to CRI to a close, at least for the moment.  It is a complex subject, but one that can come into play when dealing with any matters of color and light in the realms of photography, film, video, interior design, theater, the visual arts, and many other areas.  Good for us to have some idea of what the terms mean!

 

I hope that this series of posts on the relationship between Color and Light has helped to demystify it for you…at least to some extent. As much as we can learn, observe and discover, we will never know it all…and maybe that is as it should be.  Some things, such as the majesty and magnificence of the natural world should retain some mystery…no matter how much physics we attempt to wrap our minds around.

 

 

 

Rendering Color II

Rendering Color II

“What is color? No object of itself alone has color.
We know that even the most brightly colored object, if taken into total darkness, loses its color. Therefore, if an object is dependent upon light for color, color must be a property of light.
And so it is.”
Paul Outerbridge, Photographer 1896 – 1958

In the post, “Color Rendering I”  I delved into the nature of color and light…as Paul Outerbridge  says above,  color is a property of light…the color that we see an object as “being”, is in essence, light…the wavelengths of light it reflects, as opposed to absorbs.

In this post, I am seeking to clarify CRI…what does that mean?

CRI, or the Color Rendering Index, is a scale that measures not color, not light, but ” the ability of a light source to reproduce the colors of various objects faithfully in comparison with an ideal or natural light source”.–http://en.wikipedia.org/wiki/Color_rendering_index

The ideal or natural light source being daylight, because “it (daylight) displays (1) a great variety of colours, (2) makes it easy to distinguish slight shades of colour, and (3) the colours of objects around us obviously look natural.” —P.J. Bouma

The International Commission on Illumination  (which is usually abbreviated C.I.E.  for its French name Commission Internationale de L’Eclairage), the international authority on color, color spaces, light, and illumination, has defined CRI as the  “Effect of an illuminant on the color appearance of objects by conscious or subconscious comparison with their color appearance under a reference illuminant”.

Is the concept and definition of CRI becoming any more clear?

Trying to explain CRI reminds me of trying to translate from one language to another, in a manner that makes the meaning of a phrase in one language, comprehensible in another.  It isn’t enough just to translate the words…the whole meaning, context, and  sense of the phrase must be understood.

How’s this:

  The closer the red of your child’s red beach ball inside, under the light of say, your dining room chandelier, looks to the red the same ball appears to be outside, on the beach, under the sunlight, the higher the CRI is of that dining room chandelier illuminant.  CRI measures the ability of a light source to reveal, render, depict or show color the way daylight would.

Put another way, the color rendering index describes the  effect of a light source on how the color of an object appears to us.  It is the measurement of how much an object’s color appearance shifts when illuminated by an artificial (other than daylight)  light source compared to the color appearance of the same object when  illuminated by a “reference” light source (daylight), of comparable color temperature.

Whoops!  Color Temperature!?!  Suffice it to say, right here, right now, the CRI of a light source can only be determined when it is being compared to a reference illuminant, (natural light/daylight), with the same, or comparable color temperature.  The role of “Correlated Color Temperature”  in CRI will be discussed in a future post.

So…until then chew on the above…and I hope the light bulb goes on for you about what Color Rendering Index is.

May both your days, and nights be illuminated with light sources of the highest CRI!

Cacophony to Calm…Compensating with Color

 Cacophony to Calm…Compensating with Color

Can color “theory” heal?   If healing means balancing, compensating, and otherwise enhancing the quality of a space, object, light source, or even our bodies, then I believe it can.

Our April 17, 2011 Color Muze  on Artistically Speaking Talk Show, “muzed” about how color can be used to adjust our perception of sound, or the lack of it, and thus balance or “heal” an environment through our sense of seeing, and its potential effect on our sense of hearing.  This is an aspect of the phenomenon of “Synesthesia”, or “Unity of the Senses”, as IACC-NA (International Association of Colour Consultants/Designers-North America)  lecturer, Frank H. Mahnke, terms it.  The idea being  that our perception of color can associate with our perception of another sense, such as hearing.

Warm colors (from red to yellow-green on the color wheel), associate with loudness.

Image Source

Cool colors (from green to red-violet on the color wheel) associate with quietness.

This is reflected in our language, the way we talk about our environment, or even our feelings, in terms of color. I am not sure I have ever heard anyone refer to a quiet (or cool) red, though anything is possible!  On the contrary, I remember my mother describing feelings of anger as “Seeing red.”

By comparison, people may speak of a  quieting their emotions when they enter a room in which a “cool” blue predominates.

It is interesting to view the two together…(albeit different hues and values of red and blue).

Thus if we wish to compensate for noise problems in a space, we can add more “cooling” colors such as  blues, blue greens, perhaps even a cool blue-violet. Warm to hot colors such a saturated reds, and “hot” oranges or yellows will tend to exacerbate our sense of being in a noisy environment, which can be significant in any setting where concentration is important.

To relieve a “too-quiet” or tomb-like atmosphere in a room, and add energy, warmer (and lighter) colors may be applied, such as yellow-green, golden-yellow, reds, oranges or “hot” purples (red-violets).

It is fascinating, and fun to see the sound associations the Henrich Frieling, Director of the Institute of Color Psychology assigns to a range of colors:

Red– loud, trumpet

Pink – soft, delicate

Orange – loud, major key

Brown – dark, deep minor key

Gold-Yellow – fanfare, major key

Yellow – shrill, major key

Yellow-Green – high-pitched, minor key

Green – muffled when dull, shrill when saturated

Green-Blue – soft

Blue – distant, flute to violin

Ultramarine – dark, deep, more minor key

Violet – sad, deep, minor key

Light-Purple – weak, restrained

Crimson – powerful, stately

It really begs the question…what might a musician, singer, or music therapist have to say about this?  What about Sharry Edwards, pioneer in the study of Human BioAcoustic Biology…might she have a “color link” to her work and theories on healing the body through sound?

Perhaps a subject for another post…

Have you used color to compensate for too much noise, or not enough sound in your own or other spaces? Have you felt the effect of color healing in regards to your, or your Clients’ auditory environment?  What is YOUR experience with Synesthesia, in regards to the relationship of sight to sound, the visual to the audible?

If you feel so inspired, please share your insights with us here.  We love to hear from you.

Remember, we are all seeking the balance in this thing called Life, together.

Here’s wishing you healing wherever you need it most, in your Life right here, right now.  Cheers!