Color Temperature Matters
co-lor tem-per-a-ture: noun The temperature at which a black body radiator emits radiation of the same color as a given object.
You may or may not be able to understand the definition of color temperature, but you know it when you see it. The two luminaires in this photo both have compact fluorescent lamps in them.
Saving energy = saving money = good.
Mismatched color temperatures = bad.
The one on the left is a cooler color temperature than the one on the right. A cooler color temperature has a higher number, measured in Kelvin, while a warmer color temperature has a lower number. These two are around 3000K and 2700K. When shopping for replacement lamps, make sure to get consistent color temperatures, and decide ahead of time whether you want a warm color like incandescent or a cooler, "whiter" light.
Painting the walls a dark color, or not painting the walls at all. A key factor in the brightness of any space is the reflectances of the surfaces. The more reflective your walls, ceiling, floor, and furnishings, the less it will cost to make the room feel bright. A can of white paint is one of the most inexpensive lighting accessories you can buy.
Closing shades or draperies to keep out daylight. (Or letting the daylight in but leaving the lights on anyway.) Daylight is free, has all of the characteristics people crave in lighting - good color rendering, changing throughout the day to improve circadian rhythms, and did I mention free? Adjust the blinds to direct glare toward the ceiling, but keep the light switch off when the sun is shining.
Not using dimmers. At certain times of day or on certain days of the year people need or want more light. At other times, less is better. Dimmers save energy and increase lighting satisfaction by giving occupants control of their spaces. They're easy to install. Do it. You'll be glad you did.
Forgetting to take advantage of warranties. Sure, we've all had bad experiences with either an LED or CFL lamp. But do your research to find a high quality product from a reputable manufacturer that meets your lighting specifications. Then hold them to their warranty. If something goes wrong, don't go elsewhere. Go back to the manufacturer and get them to fulfill their warranty. That will help them improve the products in the long run, too.
Avoiding new technology. New technology does require you to understand more about lighting and the visible spectrum. You have to watch for the right color temperature and good color rendering. Lighting quality issues aren't simple. But if you choose carefully, the energy savings will be worth the extra front-end effort.
Which lighting mistakes are you making? Which is most surprising to you?
Ever wonder how they change the lamps on those super-high poles along highway interchanges?
They do NOT use a 100' ladder!
Funny Luminaire Names
I have been teaching an intro to lighting class this month (and haven't been updating the blog...whoops!) While giving the lecture on luminaires I noticed how many light fixtures are named for their shape - it's kind of fun.
Have I missed some? Does any lighting jargon make you chuckle?
It's another cloudy, snowy day here in St. Louis, and I'm longing for summer! That got me looking through some pictures from back in June, and I decided to share these two with you just for fun.
See the pole going straight up into the middle of this tree?
There's a light at the top of it!
Not much light reaches the ground, though...
Have a great weekend, be well, and create beauty!
While reading my latest issue of Natural Health Magazine, this quote from the back page caught my eye:
For many of us, Monday through Friday means slogging through traffic to sit for hours under soul-sucking fluorescents in back-breaking office chairs. But you can make your workdays healthier - mentally and physically - by making over your space with these tips.
"Oh boy!" I thought, "my magazine is going to address lighting quality. Yay!" But I went on to read suggestions that ranged from getting a fish tank or a potted plant to making ergonomic adjustments to the furniture and meditation to manage stress. No mention whatsoever of how to address the lighting quality problem. Even a paragraph about getting up and walking around only addressed the aspect of stretching. How about taking that walk outside to get exposure to sunlight? Or at least walking to a window for the emotional boost of the view?
If you find your fluorescent lighting to truly be soul-sucking, might I make a suggestion or two?
How about you? What have you done to take the "soul-sucking" out of your fluorescent office lighting?
How To Buy a Light Bulb
I was recently in one of those big box home stores helping my parents shop for things for the new house they are building. We looked at lights and ceiling fans. We checked out some electrical devices, outlets, and switches. We looked at carbon monoxide and smoke detectors - hard wired or battery powered? Dual technology or separate? We checked out some appliances. We walked all the way around the store looking for a public restroom... My point is that we were there for a while - 30 minutes or maybe an hour - when I noticed that someone in the lamp (light bulb) aisle was standing in the same place staring at the same lamps when arrived AND when we left.
It used to be so easy. The only question you had to answer when replacing a light bulb (lamp) was, "How many Watts?" But that was then. I'm here to save you a few minutes in the lamp aisle at the home store. Before your next trip, be armed with the answers to the following five questions:
1. How Bright?
Today we have to think in Lumens instead of Watts. An old 100 watt lamp produced about 1600 lumens. A 60 watt standard incandescent lamp is about 800 lumens, and 40 watt incandescent = about 450 lumens. Before you shop, know how bright you need the light to be - in lumens.
2. What Color?
Not all "white" light is the same color. For more on that topic, check out the pictures in this previous post. The point is that most of today's sources are available in different color temperatures. To most closely resemble incandescent light, select a warm hue, between 2500 and 2800 Kelvin.
3. Where Used?
This question really embodies lots of other questions. Is it in an enclosed fixture? Indoors or outside? In a transient space like a closet? Somewhere extremely hot or cold? Is it used to accent a piece of art, or does it need to be fairly shadow-free? Certain CFLs don't do well in winter temperatures, LEDs prefer the cold. Most LEDs aren't designed for fully enclosed fixtures. Many CFLs aren't either. CFLs generally take a little time to get fully bright, so they might not be the best choice for closets. LEDs tend to be very directional and better for accent lighting, but can be diffused for general lighting. CFLs are great for general shadowless illumination but are never very directional. Know where the new lamp will be used.
4. How Controlled?
Is the lamp you are replacing on a switch or a dimmer? If it is controlled with a dimmer, replacement options are more limited, and you should check dimmer compatibility before you purchase a replacement.
5. How Much Money?
Consider both initial cost and ongoing costs. To spend the least money today, buy an incandescent or halogen replacement lamp. In the long run, this choice will cost the most in energy and replacement lamps, even though the initial outlay is the smallest for this category. The middle of the road option is fluorescent. It will cost a little more today, but will last a little longer and save a little more energy than the traditional sources. Top of the line is LED. These still cost the most, but will provide the most light per watt and will last the longest...provided you buy a quality product and use it in an appropriate application.
If you head to your local light bulb store with the answers to these questions in mind, you should save yourself a few minutes. Maybe you'll even have enough time to browse the clearance aisle and get one of those inflatable snow globes at 75% off!
You Decide - 2012
Incandescent Replacement Lamps
There are three viable major categories of incandescent lamp replacements available today. Think of it like an election.
Consider all of the options and then make your selection - cast your vote. Sometimes, like in an election, you may have to pick the best of the worst...but you do have a choice, so your duty is to become informed about those options before making your selection.
This lamp type is most similar to incandescent in cost, color, physical appearance, light, dimming behavior,
technology...in nearly every way. Halogen is about 30% more efﬁcient than standard incandescent and lasts about
twice as long. The advantages and disadvantages almost perfectly align with advantages and disadvantages of incandescent lamps. They provide instant-on light. They are fully dimmable, The color rendering (CRI) is 100. With
incandescent or halogen, there are no color temperature options They do not require a ballast. They are mercury free,
TCLP and RoHS compliant. They are not sensitive to ambient temperature. They tend to be sensitive to vibration..
They produce heat when they operate. An A-lamp replacement will cost under $2 and will pay you back $3.08 in energy savings over its lifetime.
This lamp type is the one consumers are being told to use instead of incandescent. CFL is about 75% more efﬁcient
than incandescent and lasts about ten times as long. Their function is actually quite different than incandescent, but
they have been fairly common for ﬁfteen years now, so people have grown accustomed to their strengths and weaknesses. They aren’t exactly “instant-on”, but require a brief warm-up, so they are not the best option for very transient spaces or spaces controlled by occupancy sensors. They can be partially dimmable with the proper ballast, The color rendering (CRI) can be low - and that is one reason the CFL has gotten a bad reputation, but look for a CFL lamp with a CRI in the mid-80s for satisfactory color rendering.
Often I hear people say, “I just hate the color of ﬂuorescent light.” Fortunately, ﬂuorescent is available in a variety of colors. Be aware of that and be sure to get a color that you DO like. Once upon a time, lamps available in big box stores did not display the information needed to select the color. But now that is changing. Starting in 2011, the Federal Trade
Commission began requiring lamp packaging to bear a label like this:
Notice the section called "Light Appearance" which indicates how warm or cool the light looks. The warm colors more closely resemble incandescent.
This will be an even more useful tool when CRI is included, shown as “Color Accuracy” in the above DOE Lighting Facts label for LED. CFL lamps do require a ballast. They are not mercury free, but the small amount of mercury used in a high quality lamp can make it TCLP and RoHS compliant. They are sensitive to ambient temperature, and don’t operate as well in cold weather. However, there are lamp ballast combinations available that work well in temperatures down to -10 degrees F. Compared to incandescents, they are not particularly sensitive to vibration. However, if used in an application where they are turned on and off frequently (less than 3 hours per start) the lamp life will be signiﬁcantly shortened. A 100W A-lamp replacement will cost about $5 and will pay you back about $50 - $100 in energy savings over its lifetime!
While this replacement option is generally being written off by consumers as too expensive, it is an incredibly hot
item in the speciﬁcation market. LED is currently about 85% more efﬁcient than incandescent (and its efﬁcacy is still
improving because the technology is still young) and lasts about ﬁfty times as long. Unlike ﬂuorescents, they do provide instant-on light. They can be partially dimmable, typically down to 10% with the proper equipment coordination, The color rendering (CRI) is often similar to ﬂuorescent - but look for a CFL lamp with a CRI over 90 for very good color rendering. LED lamps require a driver, which is similar to a ballast. They are mercury free, and unlike all of the other lamps, they are virtually UV and IR free, so they will not fade fabrics or art. They are sensitive to high temperatures, but they love cold weather. Heat is their enemy, and the astute designer will look for good heat-sinking to ensure that LED junction temperature is maintained at its ideal level. They are not particularly sensitive to vibration. Some look yellow when they are not in use. Others are available in a more traditional looking white color. An A-lamp replacement will cost about $25 - $40 and will pay you back about $240 in energy savings over its lifetime!
This is an exciting time in the lighting industry, with the pace of change increasing exponentially! How can you possibly keep up with it all? My recommendation is to hire a lighting designer. It is my job to keep up with all of these changes, and it has been my privilege to share them with you! I believe that the importance of having a lighting designer on your projects will continue to increase as the technology changes, because lighting designers dedicate themselves to the art and technology of light, and can help you avoid the pitfalls of selecting the wrong technology or even the wrong version of the right technology.
Color is so much stranger than it seems at first glance. When we were children learning red, green, yellow, orange, blue...it seemed so straightforward. So easy to get the right answer. When did you realize that it was all a sham? An illusion? For me it happened in high school when I always wore socks to match my shirt (yea 80's!) I bought a pair of royal blue socks - perfect - until I got them home under the incandescent light. They were purple. What? Okay, then, fine. I'll wear them with my purple shirt - until - I got to school and they were blue again. How mortifying. What had happened?
Notice the cool blue color temperature in the middle of the bottom row.
In the previous post we looked at the color temperature, or color of the light. That actually has little to do with color rendering, which is the color of the objects under the light. See the difference? Either a warm source like incandescent or a cool source like daylight can render the color of objects nearly perfectly (my socks were blue under both.) It has to do with how much of the pigment is reflected back to your eye by the light source.
The three pictures above subtly illustrate differences in color rendering (or color accuracy) on the apple. The apple is the same, but it appears more pink, orange, or deep red under different lights. In the picture on the right the yellows in the apple are easier to see; In the middle picture, the dark lowlights are well defined; The one on the left seems smooth in color - neither the lowlights nor the yellows are obvious. It is important to know not only whether a source is warm or cool (color temperature) but also how it renders the objects under its light (color rendering.)
The new Lighting Facts Label (at left) required on light bulbs (lamps) sold in the US lists the color of the light, but not its color accuracy. Another new label (below) uses both. As a consumer of today's complex lighting sources, you need to know both. The color accuracy scale goes to 100. In most cases, choose the highest number you can afford. Something in the 80s for fluorescent and close to 90 for LED. If you have the opportunity to try multiple sources to see how they look in your final application, that is even better. Check color accuracy to avoid disappointment and purple...no, blue...no, purple socks - or worse!
Studies in Warm and Cool
Some encounters with color temperature. Where do you see color temperature differences in your world?
Lisa J. Reed, lighting designer and Principal at Envision Lighting Design, LLC