The Basics of Measuring Visible Light – A Primer on Photometry Tools
Radiometry is a broad field encompassing all techniques for measuring electromagnetic radiation, including the measure of visible light. These techniques measure the distribution of the radiation’s power in space. This field includes photometry, which more specifically measures attributes of electromagnetic energy that are visible to the human eye. Instruments in this category address both the broad and more specific attributes of light these fields cover.
LED Analyzers measure the luminous flux of LED lights. This means that the unit measures the total visible energy emitted by a light source. Typically, these incorporate a sphere in which the light source to be measured is placed; the sphere focuses all the power emitted from the light source directly on the detection component. Gigahertz-Optik offers analyzers with a range of different sphere sizes to meet any need.
An Illuminance Meter measures how much a given incident light illuminates a surface, unlike a luminance meter, which measures the light being emitted from a particular area. Many illuminance meters do also function as luminance meters given they use certain attachments.
Illuminance is basically another word for brightness. However the term brightness should not be used for quantitative description. Therefore we say illuminance. Today illuminance meters can effectively measure most types of visible light.
- Measuring Modes. Some meters can measure Illuminance, illuminance difference, average illuminance, illuminance ratio, integrated illuminance, and integration time. Most other meters can measure in a maximum of five modes and many often require special attachments to measure in certain modes.
- Accuracy Classification. Meters are classified by DIN and JIS standards.
- DIN classes: L, A, B, C
- JIN classes: Precision, AA, A, B
Class L and Precision are the highest classes in each, respectively. A higher class translates to greater accuracy. However, it will also mean a higher price.
- Illuminance Range. Most meters typically have a maximum range of 199,900 lx
Luminance is a photometric measurement of the luminous intensity of light travelling in a given direction. In other words, it describes the amount of light that passes through or is emitted from a particular area at a particular solid angle. This type of measurement is especially useful because it quantifies the properties of light that the human eye actually perceives. Measuring these quantities of light is essential, for example, for TV studios, sports arenas, emergency situation lighting, traffic lighting, and automobile lighting.
- Measuring Method. Luminance meters can measure either with contact or from a distance. Many can perform both, but some can only do one or the other, so choose wisely based on your needs.
- Measuring Modes. Luminance meters can measure several attributes of luminance. Typically units can measure luminance, luminance ratio, and peak luminance/luminance ratio. However, some units can measure more than just these attributes.
- Luminance Range. This is simply the range of values a luminance meter can measure. This range differs depending on measuring angle.
Established in 2004, NorthTree Associates (Cologne, MN) is a North American distributor that provides unique electronic test & measurement tools for design engineers, test engineers and production engineers. www.northtreeassociates.com