Fruit & Vegetable Lighting: When Does a Special Spectrum Make Sense?
When choosing luminaires for a supermarket or fresh-food project, specifications such as lumen output, beam angle, efficiency and CRI usually receive most of the attention.
For fruit and vegetable displays, however, another factor can make a significant difference: the Spectral Power Distribution (SPD) of the LED itself.
This is why Light4U offers a dedicated Fruit & Vegetable spectrum in selected retail luminaires. It is designed specifically for the broad mix of colours found in fresh produce rather than behaving like a conventional 3000K white LED.
Both are 3000K. So what is different?
On a basic specification sheet, the difference may appear small.
Our measured Fruit & Vegetable module has a colour temperature of 3001K and CRI 94.9. A standard 930 module used for comparison measured 3131K and CRI 94.0.
Both can therefore be described as approximately 3000K with CRI 90+. Based only on these two values, you could expect similar colour reproduction.
The spectral graphs show that this is not the case.
The Fruit & Vegetable module has a deliberately different spectral distribution, with a strong and broad contribution through the orange-red part of the visible spectrum. This influences how strongly different colours in the products are reflected back to our eyes.
What do CCT, CRI, R9, Rf and Rg actually mean?
To understand the difference, look beyond the two values most commonly shown on a luminaire specification sheet.
CCT – Correlated Colour Temperature
CCT describes the general appearance of white light, expressed in Kelvin. A lower value looks warmer, while a higher value appears cooler. However, CCT does not describe the complete spectrum. Two LEDs can both be around 3000K while producing different amounts of energy at individual wavelengths.
CRI – Colour Rendering Index
CRI indicates how faithfully colours are reproduced compared with a reference source. The commonly stated CRI or Ra value is calculated from test colours R1 to R8. A value close to 100 indicates high general colour fidelity.
This is useful, but it doesn’t tell the full story for retail applications because the average CRI value doesn’t fully represent strongly saturated colours.
R9 – saturated red
R9 is one of the additional CRI test colours and represents strong red. Importantly, R9 is not included in the standard CRI Ra average.
This means that two LEDs can have almost the same overall CRI while performing very differently on saturated red products such as tomatoes, red peppers, strawberries or red apples.
TM-30
TM-30 is a more detailed method for evaluating colour rendition. Instead of relying on only a small number of test colours, it evaluates 99 colour evaluation samples distributed across the visible colour space.
Two of its most useful values are Rf and Rg.
Rf – Fidelity Index
Rf describes how closely colours under the tested light source match the reference source. A higher value means greater colour fidelity. An Rf close to 100 means colours remain very close to the reference.
Rg – Gamut Index
Rg describes the average change in colour saturation, or chroma.
- Rg around 100 means average colour saturation is similar to the reference.
- Rg above 100 indicates increased average colour saturation.
- Rg below 100 indicates reduced average colour saturation.
Rg therefore tells us something that CRI alone cannot: whether colours are being rendered with more or less visual intensity.
The comparison becomes much clearer
| Parameter | Fruit & Vegetable | Standard 930 |
|---|---|---|
| CCT | 3001 K | 3131 K |
| CRI | 94.9 | 94.0 |
| R9 | 97.1 | 59.7 |
| TM-30 Rf | 91.8 | 91.6 |
| TM-30 Rg | 106.7 | 100.3 |
The first important point is that Rf is almost identical: 91.8 for Fruit & Vegetable and 91.6 for the standard 930.
In other words, the specialised module does not achieve its effect simply by sacrificing colour fidelity.
The significant difference is Rg. The standard 930 measures 100.3, almost exactly neutral in average saturation. The Fruit & Vegetable module reaches 106.7, showing that its spectrum intentionally increases colour saturation and separation.
The TM-30 analysis goes even further by dividing the colour space into 16 hue bins. In the Fruit & Vegetable measurement, several colour regions show positive chroma shifts of up to approximately 8%. This tells us where the increased gamut is actually occurring instead of reducing everything to one average value.
R9 shows another major difference
The contrast is even greater when we look specifically at saturated red.
The Fruit & Vegetable module achieves R9 97.1, while the standard 930 example measures only R9 59.7.
This is particularly relevant for tomatoes, red peppers, strawberries, apples and other fresh products where rich red tones contribute strongly to their visual appearance.
The interesting point is that both LEDs still have an overall CRI around 94–95. Looking only at CRI would therefore hide a very significant difference in their red rendering.
What does the spectrum itself show?
The SPD graph shows how much optical energy the LED produces at different wavelengths across the visible spectrum.
A conventional 930 LED is designed primarily to provide balanced, high-quality warm white light. The dedicated Fruit & Vegetable module has a different spectral shape, including a much broader and stronger contribution in the orange-red region.
This is important because objects do not create their own colour. They absorb some wavelengths and reflect others. A red tomato can only reflect red wavelengths that are actually present in the incident light.
By changing the spectral balance, the LED can therefore influence how strongly individual colours appear without changing the physical product itself.
What about Duv?
Another parameter visible in the measurements is Duv. This indicates how far the white point lies above or below the black-body locus.
The standard 930 example measures Duv +0.0005, placing it almost directly on the black-body locus. The Fruit & Vegetable module measures Duv -0.0124.
A negative Duv shifts the visual character away from yellow-green and towards a more pinkish or reddish appearance. In this specialised module, that characteristic works together with the spectral distribution to support the intended fresh-produce presentation.
What does this mean when specifying a project?
For general circulation areas in a supermarket, a standard 830 or 930 LED can be completely suitable.
A dedicated fruit and vegetable department has a different objective. Here, the lighting becomes part of the visual presentation of the products.
The luminaire optics determine where the light is directed. The LED spectrum determines how the colours within that beam are rendered.
A Fruit & Vegetable spectrum therefore makes particular sense when:
- fresh produce is an important visual area within the store;
- many saturated colours are displayed together;
- strong colour differentiation is desirable;
- the lighting concept uses accent lighting to highlight the products.
Choosing the spectrum together with the luminaire
Selecting a retail luminaire should therefore involve more than wattage, lumen output, beam angle and a general CRI value.
Two luminaires can both be described as approximately 3000K, CRI 90+ while producing noticeably different results on the same products.
The Light4U Fruit & Vegetable spectrum combines high overall fidelity with an increased colour gamut and very strong saturated-red reproduction.
For the right fresh-produce application, specifying the spectrum together with the luminaire and optics gives the lighting designer considerably more control over how the complete display is perceived.
