GENERAL LIGHTING MEASURING IN LAB
SPECTROMETRIC and SPECTRORADIOMETRIC MEASUREMENTS
Spectrometric Measurements System, Recommended product: new Specbos 2501 with two accessories (Integrating sphere, CIE 127 cond. A/B set up)
The following four basic quantities exist in light measurement and can be measured with a complete specbos 2501 system:
| Quantity | Symbol | Unit | Simplified definition | Used to characterise … |
| Luminous flux |  |
lm | “optical power” into all directions | Halogen lamps, LEDs |
| Luminous intensity |  |
cd (basic unit) |  |
Point like sources as LEDs and lamps with reflector |
| Luminance |  |
cd/m2 |  |
Homogenious sources as monitors and video walls |
| Illuminance |  |
lx |  |
Brightness in a certain plane |
A street lamp emits a luminous flux (Φv), and part of this flux is radiated into a specific angle (Ω). The quotient of this flux is the luminous intensity (Iv), which determines how much light is directed in a given direction.
This intensity then creates the illuminance/irradiance (Ev) on a specific area of the street. Together with the street’s reflectivity, this value generates the luminance (Lv), which is the visual impression of the street for an observer.
Photometric and Radiometric Quantities
These four quantities—luminous flux, luminous intensity, illuminance, and luminance—can also be considered as radiometric quantities, which are physical properties not directly related to human vision. These quantities can be measured either as spectral quantities (per nanometer) or as total quantities (summed over the entire wavelength range).
For a more detailed explanation, see the extended scheme of photometric and radiometric quantities in Technical Note 20.
Spectral Measurement with the Specbos 2501 System
A Spectrometric Measurements System measures the spectral radiometric quantities within its operational wavelength range. This spectrum is then used to calculate all photometric, total radiometric, and other quantities.
The basic unit, the specbos 2501 spectroradiometer, can measure both spectral radiance and spectral irradiance. It can be paired with an integrating sphere for flux measurements and with a CIE 127 setup to measure the radiant intensity of LEDs. Additionally, the spectrometer can use irradiance data and apply the inverse square law to calculate radiant intensity (see the application on radiant intensity calculation using irradiance measurement).
Thus, the specbos system covers all spectral spot measurement applications in laboratory settings, making it ideal as a fundamental piece of laboratory equipment.
Application tools
Here is a list of all the equipment for this applications.
