Redefining White

January 29, 2013 / no comments

I remember my first trip to Paris, The City of Lights. But, because I’m a lighting nerd, I couldn’t help finding the yellow headlights on automobiles particularly striking. Probably because it was so different from the headlights I was used to in the United States at the time. Today, however, I’m seeing more and more headlights in the blue range as opposed to the standard incandescent halogen range of about 2900K. Do we see better under cool light, or is it simply a function of the electric source generating the light? Up until the 1940’s or thereabouts, ‘white light’ for interior architectural applications has had a predominantly warm cast to it, mostly because it was generated by candles or incandescent sources. Since World War II and the widespread use of fluorescent sources, we’ve seen our interiors take on cooler color temperatures. With the advent of LED light sources, it is more efficacious to generate light in the blue range than in the warm range. Are we looking at an even ‘cooler’ future in architectural lighting?

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The Color of Light

November 15, 2010 / no comments

Despite some of their current shortcomings, we are all enamored with the hope and promise of LEDs. When we begin a design session with a client these days, it’s a matter of minutes until someone asks “can we use LEDs for that?!” We respond with the usual overview that there are some very good LED products on the market now, but there are also a lot of poorly-made products, snake-oil sales claims, and companies without a proven track record. In essence, “proceed with caution” is our approach.

One of the things that has bothered me most about LED fixtures is their visual color temperature. The products that I have seen and tested give off a light that is too cool for my preference. But, the world is changing and perhaps my perspective is starting to change a bit too. The following is A Tale of Two Task Lights: a Recently Acquired Fixture and the Lessons Learned.

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Good tales often begin with a historic perspective, and so shall this one. Throughout the ages, people have associated low-level lighting with the warmth of firelight or of a candle. I confess that I love the warmer color temperature of a halogen task light. My desk lamps and even the under-cabinet lighting in my kitchen have always been halogen.

The indirect fluorescent lighting that I also have in the kitchen provides a very energy-efficient and comfortable ambient light level in the evenings, but the color does not deliver the same warm glow as the halogen. When the under-cabinet halogen lights are dimmed, they get even warmer and more ‘buttery’. I have yet to achieve that same warm, low light level with LED, compact fluorescent, or linear fluorescent products.

From among the outpouring of new LED products, I purchased my first LED task light this year. I did this to begin to wean myself off of my halogen diet, or at least to try in good faith to live with this new technology. Perhaps it also relates to the overall picture of striving to live healthier and in a more sustainable way. I suppose a parallel could be made with eating healthier – using less butter and more olive oil, for example. Yes, I started to compost as well.

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I put my 50-watt, 2850K halogen task light into storage, and began to use my sleek new 9-watt LED desk fixture. The color temperature is specified at 3000K. For the first month or two I had a knee-jerk negative reaction whenever I turned it on. Too cool – as in temperature, not hip factor. I missed that warm buttery glow. However, over the course of a few months, I am beginning to grow accustomed to its cooler cast. The fixture has excellent glare control and the output is comfortable. If the fixture produced glare, or was either too dim or too bright, those factors would have certainly biased me against the LED task light. But I couldn’t find fault with it in those areas.

It has been about six months and I am now acclimated to the light quality of my new task light. I enjoy using it and the color temperature has sort of grown on me. Does making healthy choices involve accommodation and adjusting our standards, or is it the retooling our thinking and attitudes, which open us up to new options?

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I believe that, as LEDs become more widespread in offices and homes, retail, street lighting, parking garages, etc. in the next few years, their shortcomings – particularly in the area of color temperature and glare control – will cause a backlash among users. The marvels and mysteries of LEDs as the great hope for our future will be tarnished by products that don’t live up to their promises and our expectations. While I do believe that the industry will have to deal with these shortcomings, what I have learned is that people are surprisingly adaptable to new technologies.

The visual issues that manufacturer’s have been dealing with – glare, multiple shadowing, effective dimming, cooler color temperature, and that strong desire for warmer color temperatures when dimmed – will get worked out over time as we grow accustomed to a new light.

Photo Credits: Schani (1), Lam Partners (2, 3)

Perception and Expectation

September 21, 2009 / no comments

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Light and color have historically been closely integrated with architecture and design, as they can completely change a viewer’s perception of form and space. Color around us is the simple consequence of reflected or transmitted light. It is not a characteristic of an object without light.

In Monet’s study of the Rouen Cathedral, his painting series depicts a perception of the Cathedral that dramatically changes as the lighting quality and colors vary. These different perceptions of the same Cathedral are due to the reflections of light, color, and relative brightness of the architectural form, caused by varying daylight conditions.

Light is a very descriptive tool: it creates shadow and depth, defines edges and boundaries, renders objects and people, and informs us of the conditions of our surroundings. With shifts of light, brightness/contrast ratios, and changing reflections, the “image” of the space transforms. This image or “perception” of space is an important biological need for humans, giving us not only the ability to perform specific tasks within that space, but also the important quality of visual, aesthetic, and psychological comfort.

Appropriate color of light is very important to the quality of lighting in a space. As humans, we have developed subjective expectations of what is appropriate, based upon previous experiences that have been mentally compiled. We process our visual field in comparison to other spaces that are “pleasing,” as well as to what we know of the exterior environment of that particular time of day or season. It’s important to recognize the change in color and intensity of light, from day to night and summer to winter, in artificial lighting designs, as those expectations are firmly set in our circadian rhythms.

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The Amenity Curve, developed by A.A. Kruithof, illustrates the idea that a “visually pleasing environment” is directly related to the “expected” color temperature of the light source. Typically, we expect lighting color temperatures in the warmer range for spaces with lower overall light levels, such as residential environments or lounge areas, whereas cooler color temperatures are expected for more public spaces that require higher light levels. “Warm” refers to light color temperatures between 2700K to 3000K. Incandescent sources are rich in red and yellow, which is similar to the familiar light of the sun, and of common candle flames. “Cool” refers to light color temperatures between 3600K to 5500K. These color temperatures are more closely related to the bluish color of skylight, around 6500K.

When our visual expectations and our need for information are satisfactorily met, then our environment is perceived as appropriate and comfortable, meaning that we measure “comfortable” lighting not by a strict allowance of footcandles, but as a balance of brightness and contrast throughout a space that meets our expectations, both physically and mentally.

These principles of light and color in architecture are the means by which architecture expresses its form and function to its occupants. Light communicates visual information to the viewer, and establishes how we perceive our environment.