Some people claim to get headaches from cooler color temperatures, others from warmer color temperatures. Research in this field is still ongoing and there is a lot of conflicting information out there. One thing we will mention is that the American Medical Association recommends staying away from light above 5700K as it can be detrimental to human circadian rhythm and affect sleep patterns.
Again, these are just common uses, some people do prefer to have a 5700K in their home and others may prefer 3000K for LED wall packs on the side of their building. For retail sales, bright is good to show of the products being sold. Retail lighting is usually 4000K-5700K and more than often on the cooler side as the cooler color temperatures typically have a slight advantage in lumen output over a warmer color in the exact same wattage. Business office lighting is usually around 4000K. Lighting we often see in residential use is more relaxed settings are usually 3000K-4000K. In general, most warehouse lighting and outdoor lighting is 5000K, often called bright white as it's a close representation of sunlight. Shows that LEDs in general have some work to do to get to R9 standards above 70+, and also why the R9 metric is not listed on many lights yet.Ī: Color temperature is mostly a matter of preference. To give some perspective, standards such as Title 24 in California, Well building standards and the GSA (government services agency) are requiring only CRI 80+ and R9 of 50+. Most R9 in general LED is closer to 40-50.
Grow lights require a full spectrum, known as PAR for best results. In this chart we see the light is about 4100 kelvin and 93 CRI, The R9 drops to 75, which is actually excellent because this is a grow light. Now most lighting spectrum charts will generate all the data. Here is an example where the CRI would be high, but the low R9 does not tell the whole story. The perfection is also known as sunlight.
Generally incandescent is the benchmark or reference light (black body radiator in the lab, but that's a much longer article) but really the 100 score on an R15 measurement would be perfect. So you have to do all well to score very high. Whether its CRI., R9 or R15 the numbers are an average. For designers and users anyway, less so for manufacturers as we'll get to below.Ī: R9 is calculated as a average of R1-R9, which is the pastel color group up to red. R9, however adds that important Red color which is why its becoming a more preferred metric in lighting. You can see that CRI uses a limited, albeit critical part of the scale. Here is how CRI, R9 and R15 are calculated. Thus colors with red in them will show much better in a high R9 score. ( For reference solid saturated colors are R9-R12 and earth solids are R13 to R14) The big one, however, is R9 because that is red! R9 is one better than CRI because it adds the all important Red spectrum. Since R10-R15 are generally not an improvement in color reproduction, those are skipped. CRI is a 1960 standard, but in reality there are 15 color bands, these are referred to as R15. The higher the CRI the better those colors show. Incandescent and halogen do a good job of color rendering (CRI 95+), where HID sources typically are low color rendering (sub 50 CRI)ĬRI is based on the R1 to R8 colors only, also known as the pastel colors. Just because a light is white does not mean that colors will show true underneath it. A: CRI (color Rendering index) and R9 (average of R1-R9) reflect how well a light will reproduce colors.