by Stan Walerczyk, HCLP, CLEP
If you really want to be a lighting expert and have an advantage over your competition you need to invest in at least one spectrometer and train your outside sales people how to use it.
Correlated color temperature (CCT), Kelvin, scotopic/photopic (S/P) ratios and color rendering index (CRI), which are just pastel colors, are no longer sufficient.
Good spectrometers can provide that information as well as spectral power distributions (SPDs) and histograms including bright and earth tone colors, so you can provide accurate color matching and design optimal Human Centric Lighting.
Although the fluorescent on the left and the LED on the right are both 3500K, spectrometers show you that they highlight same colors quite differently.
Also various fluorescent lamps at any one CCT or Kelvin can have quite different SPDs, and various LEDs at any one CCT or Kelvin can also have quite different SPDs. For example an LED product with red, green and blue (RGB) LEDs have quite a different SPD than an LED product with typical blue pumped white LEDs at the same CCT or Kelvin.
Below shows the pastel colors in CRI, which are R1 – R8, R9 – R12, which are bright colors, and R13 – R14, which are earth tones. What good is CRI if you need to shine light on bright or earth tone colored objects? Also LEDs often do a better job with bright colors than pastels.
For Human Centric Lighting, the general rule of thumb is substantial 460 – 490 nm light most of the day, especially in the morning to suppress melatonin production, and very little of that one to two hours before going to bed. Proper lighting can improve circadian rhythms, alertness, sleep, mood, visual acuity, perception and performance – productivity.
The following diagram has an SPD and histogram of a 6500K LED troffer from a spectrometer. You can see that it has substantial 460 – 490 nm content, so it would be good most of the day. You can also see the R1 – R15 histogram, showing a good amount of all colors except for red. R15 is for Japanese complexion, which is often not that important. Ra is basically CRI, based on R1 – R8 pastel colors. Re is the average of R1 – R15.
Some large utilities, at least in California, have spectrometers in their tool lending libraries, which people can borrow at no cost.
But even if you have to buy one at about $2000, it is probably a very good investment, because it can help improve sales compared to your competitors, who do not have a spectrometer.
There are several manufacturers and models, and I have not tested them all. At this time my favorite is the Lighting Passport Spectrometer Standard Set.
Walerczyk is principal of Lighting Wizards, an independent energy efficiency consulting firm. He has over 25 years of lighting experience including distribution, maintenance, retrofit contracting, and industry research. An Association of Energy Engineers-Certified Lighting Efficiency Professional, he also holds a Lighting Certified designation from the National Council on Qualifications for the Lighting Professions. He can be reached at firstname.lastname@example.org.