The color rendering index indicates how faithfully colors are rendered under a lamp. It is an average of eight test colors, and precisely the colors you need outdoors are not included.
In industry, this is not an aesthetic question. A technician who has to read a wire color, a sorter who separates a material stream, a painter who has to match a color: those are all three color rendering. Below is what Ra measures, what R9 and TM-30 add to that, and what value your application requires.
The index calculates eight test colors, R1 to R8, and takes the average of them. Saturated red, R9, is not included in that. A luminaire can therefore achieve an Ra of 80 and at the same time render red so poorly that a red blood vessel looks brown.
Ra ranges from 0 to 100, where 100 represents rendering identical to the reference source. For outdoor and site lighting, only the upper part of the scale is relevant, and higher is not always better: a high Ra typically comes at the expense of efficacy.
Five places where high color rendering is not a convenience, but a prerequisite to be able to do the work or perform inspections.
In a spray booth or during final inspection, color rendering is part of the process: a color deviation that is not spotted there will surface at the customer's end. If cameras or vision systems are also used in such an area, ask for a flicker-free driver: flicker that the eye cannot see will interfere with an image capture or measurement.
One point belongs on the table first when it comes to a spray booth, and is independent of color rendering: the room itself places demands on the fixture, including explosion safety. We do not supply ATEX fixtures. If that is an issue for you, discuss it before talking about Ra.
Four situations on a site or in a hall where a low color rendering is not inconvenient but unsafe.
The index is from 1965 and is intended for incandescent and gas-discharge lamps. With LEDs, it is reaching its limits, which explains why two luminaires with the same Ra can look different.
The index counts eight pastel colors, R1 to R8. Saturated red is R9 and is not included in the average. With LEDs, that is precisely the color that is most often lacking, so a luminaire can achieve an Ra of 80 with a poor R9. Request that value separately.
Ra measures the deviation from a reference source, not its direction. Two luminaires with the same Ra can shift colors in opposite directions, and you will notice that immediately when they are placed side by side.
Light can render colors faithfully yet dulously. The more modern TM-30 method splits that into two numbers: Rf for fidelity and Rg for saturation. Ask for TM-30 if you really want to put two fixtures side by side.
The entire index is determined at high light levels. In an area with 20 lux, the eye operates in the twilight zone, where color sensitivity decreases and shifts toward blue. A high Ra therefore yields less at such levels than the number suggests, and the light level itself is more important than the index. That is why we first discuss how many lux the work requires and then which color rendering belongs with it.
Practically speaking: use Ra to agree on a lower limit, bring in R9 as soon as color safety or camera footage is involved, and ask for TM-30 if you really want to place two luminaires side by side. And when in doubt, show it rather than measure it: testing a luminaire on-site for one evening answers the question definitively.
The color rendering is listed per version on the datasheet, along with the color temperature. If your application requires a higher Ra or a specification of R9, please state this when making the request: that is a design choice for the version and not a different fixture.
If you are in doubt whether the color rendering is suitable for your work, request a trial luminaire. For the corresponding choice in color temperature, everything is listed on Light color and Kelvin, and for the light level on luminous flux and luminous intensity.
Not “as high as possible”, because a higher Ra costs yield and therefore energy. These four questions lead to the value that belongs to your work.
With LED, a higher color rendering is achieved with a broader spectrum, and that comes at the cost of efficiency: within the same LED family, stepping up to a higher Ra typically results in a loss of a few percentage points in lm/W. That is no reason to ignore Ra, but it is a reason not to demand a higher value than the work requires.
In an area where no one has to evaluate colors, that yield is worth more than a higher number on paper. In a sorting hall or with a camera, it is the exact opposite.
How large that difference is per series exactly varies per LED family and per model. Request this if the choice comes down to a few percent; we will then include it in the lighting calculation.
What 3000, 4000, and 5700 K do outdoors, and where amber and dark sky belong.
Why more lumens does not mean more light on the ground.
The limit values per zone, the rules per European country, and why full cut-off means 0% upwards.
All subjects together are on subsidy and knowledge base.
If it concerns a normative requirement from a federation or a client, please include that requirement. Then we will state which implementation meets it, rather than mentioning a number.
The color rendering index: a measure of how faithfully colors are displayed under a light source, on a scale up to 100. The value is the average of eight test colors, R1 through R8. Ra 100 means rendering identical to the reference source.
R9 is saturated red, and that color is not included in the average of Ra. With LED, red is precisely the color that falls short most often, so a luminaire can achieve Ra 80 and render red poorly. As soon as color affects safety or camera footage, you should request the R9 value separately.
Color temperature, in kelvin, indicates the tint of white the light has. Color rendering indicates how faithfully colors are displayed under that light. Two 4000 K fixtures can have a very different Ra. They are completely independent of each other, and both should be listed on a datasheet.
In practice, Ra 70. That is sufficient for driving, walking, loading, and recognizing. Ra 80 is appropriate when color is part of the work: sorting, assembling, inspecting, or reading core colors. Ra 90 remains reserved for areas where color itself is the product, such as a paint booth or an inspection table.
CRI 90 or higher, and including the R9 value. In a spray booth or finishing room, a color deviation must be visible before the work leaves the facility, and red in particular, along with color saturation, are decisive for this. This is one of the few applications where the efficiency loss of a broad spectrum is indisputably worth it. Please note: a spray booth also places demands on the fixture that have nothing to do with color rendering, including explosion safety. We do not supply ATEX fixtures.
No. A higher color rendering is achieved with a broader spectrum, and that costs a few percentage points of lm/W. On a large site with many operating hours, you pay for that every hour, while no one is evaluating colors there. Choose the value for the work, not for the number.
A more modern method that splits color rendition into two numbers: Rf for fidelity and Rg for saturation. Ra gives a single average, thereby concealing the direction of the deviation. If you really want to compare two luminaires side by side, ask for TM-30.
Because those lamps have a very narrow spectrum: almost exclusively orange light. The Ra value is around 20 to 40, which means that colors are practically indistinguishable. During a replacement, it is the first thing technicians notice, even before the difference in light level.
Less than the number suggests. The index is determined at high light levels; on a site with 20 lux, the eye operates in the twilight zone, where color sensitivity decreases. At low levels, the light level itself is more important than the index.
Yes, and that is the fairest way. We place a trial fixture on your site or in your hall, so that you can judge for yourself whether core colors, material flows, or faces are easily readable. A screenshot cannot reproduce color rendering; your eyes can.
We will place a trial fixture on your site or in your hall so that you can see whether wire colors, material flows, or faces are clearly visible. You will also receive a free lighting calculation and a response from an engineer within one working day.
