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Color Temperature (K) & Color Rendering (CRI)

What is Color Rendering Index (CRI)?

Color rendering describes how a light source makes the color of an object appear to human eyes and how well subtle variations in color shades are revealed. The Color Rendering Index (CRI) is a scale from 0 to 100 percent indicating how accurate a "given" light source is at rendering color when compared to a "reference" light source.

The higher the CRI, the better the color rendering ability. Light sources with a CRI of 85 to 90 are considered good at color rendering. Light sources with a CRI of 90 or higher are excellent at color rendering and should be used for tasks requiring the most accurate color discrimination.

It is important to note that CRI is independent of color temperature (see discussion of color temperature). Examples: A 2700K ("warm") color temperature incandescent light source has a CRI of 100. One 5000K ("daylight") color temperature fluorescent light source has a CRI of 75 and another with the same color temperature has a CRI of 90.

To further understand the physics of color rendering, we need to look at spectral power distribution.

The visible part of the electromagnetic spectrum is composed of radiation with wavelengths from approximately 400 to 750 nanometers. The blue part of the visible spectrum is the shorter wavelength and the red part is the longer wavelength with all color gradations in between.

Spectral power distribution graphs show the relative power of wavelengths across the visible spectrum for a given light source. These graphs also reveal the ability of a light source to render all, or, selected colors.

Below see how a typical spectral power distribution graph for daylight.

Notice the strong presence (high relative power) of ALL wavelengths (or the "full color spectrum"). Daylight provides the highest level of color rendering across the spectrum.

Compare the daylight spectral power distribution with that for a particular fluorescent lamp.

The most obvious difference is the generally lower level of relative power compared to daylight - - except for a few spikes. All wavelengths (the "full spectrum) are again present but only certain wavelengths (the spikes) are strongly present. These spikes indicate which parts of the color spectrum will be emphasized in the rendering of color for objects illuminated by the light source. This lamp has a 3000K color temperature and a CRI of 82. It produces a light that is perceived as "warmer" than daylight (3000K vs. 5000K). It's ability to render color across the spectrum is not bad, but certainly much worse than daylight. Notice the deep troughs where the curve almost reaches zero relative power at certain wavelengths.

Here is another fluorescent lamp.

This spectral power distribution looks generally similar to the one above except it shows more power at the blue end of the spectrum and less at the red end. Also, there are no low points in the curve that come close to zero power. This lamp has a 5000K color temperature and a CRI of 98. It produces light that is perceived as bluish white (similar to daylight) and it does an excellent job of rendering colors across the spectrum.

Above are links to linear and compact fluorescent light bulbs that have a CRI of 90 or higher. If you want a high color rendering bulb to produce light perceived as warm white, choose a bulb with a color temperature of 3000K or 3500K. If you want a high color rendering bulb to produce light perceived as white, choose a bulb with a color temperature of 4000K. For a bulb that simulates daylight, choose a color temperature of 5000K or higher.

Note: all incandescent and halogen light bulbs, by definition, have a CRI close to 100. They are excellent at rendering color. However, except for some halogen bulbs, most incandescents produce a warm 2800K color temperature. The only way to achieve the bluish white appearance of daylight with incandescent bulbs is to use bulbs coated with neodymium. However, these bulbs have a CRI much lower than 90. They are not good for accurate color rendering across the spectrum.

1. OVERSEAS AGENTS WANTED

Ⓐ Have potential marketing channel and sales network in local Lighting field.

Ⓑ Familiar with local marketing situation, and know well about the operation/marketing process of local LED and Lighting brands.

Ⓒ With resource and capability enough to expand market and glad to promote WASKONT Lighting products in local areas.

2. DISTRIBUTORS WANTED

Ⓐ Familiar with LED and Lighting field.

Ⓑ Have some marketing experience in Lighting or other electrical or technical products.

Ⓒ Undertake sales tasks, have high responsibility and work hard.

Main questions for better understanding:

1. Did you prepare LED product range for your local market?
2. Which products will be more interesting in your market?
3. What is more important for your market: low price or best quality?
4. Did you check all competitor`s prices?
5. Do you understand about way of delivery and customs taxes?
6. Which Certificates do you need?
7. Do you find place for store or warehouse?
8. Who will be your main clients?

If you have any interest, please send your information to e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

LED Technology

LEDs are light emitting opto-electronic semiconductor components. Since decades, they are used in the field of man-machine communication to convert electrical signals into visual information.

Typical LED applications encompass household appliances, telecommunications, life sciences and signal technologies. Moreover, due to its low power consumption and excellent operational reliability LED technology partly replaces conventional lighting solutions already today.

The development of LED technology progresses at rapid pace, as light efficiency (Lumen/Watt) increases, colour qualities improve and temperature ranges get manageable. Consequentially, new territories of applications will open up, especially in the field of standard lighting.

Based on their structure, LEDs can be split into groups:

Light Technology

Light technology. covers the generation and application of light as well as lighting technology and methods and processes of light evaluation, i.e. the measurement of light-related parameters; these include illuminance, luminance, and luminous intensity.

Illuminance Ev

Illuminance Ev is defined as the areal light flux density on a lighted area hit by the luminous flux Fv. Illuminance is measured in lux (lx=lm/m²), where luminous flux and area are put in as [lm] and [m²], respectively. Based on the illuminance Ev, a specific lighting solution can be calculated and designed.

Luminance Lv

Luminance is defined as the areal density of luminous intensity of a light emitting or reflecting area which radiates the luminous intensity Iv at a given angle. Luminance Lv is measured in [cd/m²].

Luminous intensity Iv

Luminous intensity Iv [cd] is among the key parameters describing an LED or LED display. It is defined as the luminous flux emanating from a point source within a solid angle W (steradian) into a particular direction. Hence, luminous intensity is the directional luminous flux Fv within a solid angle W. Today's LEDs achieve a luminous intensity of Iv=10 cd or more. As intensity depends on the radiation angle, an LED chip equipped with a 30° reflector achieves a higher luminous intensity than an identical LED chip with a 60° reflector. That is, using a 60° reflector the same luminous flux Fv has to illuminate a larger area than using a 30° reflector.

In addition to these parameters, VS Optolelectronic's in-house photometric laboratory is equipped to analyse all photometric, colorimetric and radiometric characteristics. Two in-house Gonio spectrum radiometers exactly determine the radiation characteristics of LEDs and LED light modules of up to 350 mm Φ.

LED-Technology eco-friendly and eddective

• LED lighting system saves electrical power !
• 80% compared to incandescent bulb
• 50% compared to compact fluorescent lamp
• 60% compared to fluorescent lamp
• 75% compared to halogen lamp
• 80% compared to mercury-vapor lamp
• 65% compared to high pressure sodium lamp

Long life and cost saving with green energy!

• LED Light sources are directional light sources
• LEDs offers up to 100 lumen/W compared to HPS with 140 lumen/W.
• The lifetime for LEDs with only low operating voltage is 3-4 times higher than HPS Lighting.
• HID (High Intensity Discharge) Lighting creates EMI problems.
• LED is a cold light source (with none UV and FIR) and does not pollute the environment.
• All HID Lamps have a light-derating after 2.000 operation hours
• LED does not have any derating up to 50.000 hours @ 20°C Tamb