{"id":412,"date":"2026-04-15T15:22:32","date_gmt":"2026-04-15T13:22:32","guid":{"rendered":"https:\/\/agrolux.provesonlinevalles.com\/?page_id=412"},"modified":"2026-05-18T06:59:47","modified_gmt":"2026-05-18T04:59:47","slug":"light-terminology","status":"publish","type":"page","link":"https:\/\/agrolux.provesonlinevalles.com\/nl\/knowledge\/light-terminology\/","title":{"rendered":"Lichte terminologie"},"content":{"rendered":"
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Lichte terminologie<\/h1>\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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Light - terminology\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t
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When discussing light, various terms are commonly used, such as PAR, PPFD, and DLI. Below, we explain what they mean.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t

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Figure Sensitivity to light spectrum <\/em>The sensitivity of plant photosynthesis to light of different wavelengths (left) and the sensitivity of the human eye to the light spectrum (right)<\/em><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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\n\t\t\t\t\t\t\n\t\t\t\t\t\t\tPAR\t\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/h3>\n\t\t\t\t\n\t\t\t\t\t\t\t\t\t

\n\t\t\t\t\t\tPAR stands for photosynthetic active radiation, which refers to radiation that can be utilized for photosynthesis. Plants can only use specific wavelengths of light for photosynthesis, namely those within the range of 400 to 700 nm. This includes blue light (400 \u2013 500 nm), green light (500 \u2013 600 nm), and red light (600 \u2013 700 nm).\n\n\t\t\t\t\t<\/p>\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\t\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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\n\t\t\t\t\t\t\n\t\t\t\t\t\t\tPPF and PPFD\t\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/h3>\n\t\t\t\t\n\t\t\t\t\t\t\t\t\t

\n\t\t\t\t\t\tPPF stands for Photosynthetic Photon Flux, representing the quantity of photons in the PAR region of light. It is used to indicate the amount of light emitted by a light source per second, measured in \u00b5mol\/s. To determine the light received by a plant, the photon flux density in the PAR spectrum must be assessed. This is the Photosynthetic Photon Flux Density (PPFD), denoting the amount of photosynthetically active photons per square meter per second. The unit of PPFD is \u00b5mol\/m2\/s.\n\n\n\t\t\t\t\t<\/p>\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\t\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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\n\t\t\t\t\t\t\n\t\t\t\t\t\t\tDLI\t\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/h3>\n\t\t\t\t\n\t\t\t\t\t\t\t\t\t

\n\t\t\t\t\t\tThe total amount of PAR light a crop receives in a day is also referred to as the daily light integral (DLI). DLI is measured in mol\/m2\/day. You can calculate DLI by multiplying the PPFD by the day length (and adjusting for units). For example, if a lamp emits 100 \u00b5mol\/m2\/s and is on for 12 hours, the DLI would be: 100 * 12 * 3600 \/ 1000000 = 4.32 mol\/m2\/day.\n\n\n\n\t\t\t\t\t<\/p>\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\t\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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\n\t\t\t\t\t\t\n\t\t\t\t\t\t\tLight units\t\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/h3>\n\t\t\t\t\n\t\t\t\t\t\t\t\t\t

\n\t\t\t\t\t\tVarious units are used to express the quantity of light, such as \u00b5mol\/m2\/s, W\/m2, or Lux. While it is relatively straightforward to convert a quantity like distance between different units, the same is more complex for light. In the next paragraphs, we explain the units, how to convert between them, and why certain units are not recommended in horticulture.\n\n\n\n\n\t\t\t\t\t<\/p>\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\t\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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\n\t\t\t\t\t\t\n\t\t\t\t\t\t\tJoule\t\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/h3>\n\t\t\t\t\n\t\t\t\t\t\t\t\t\t

\n\t\t\t\t\t\tJoule (J) is the unit of energy, and Watt (J\/s) is the unit of power (energy per unit time). In (assimilation) lighting and natural radiation, these units indicate how much energy the photons from a light source carry. This allows the calculation of their impact on the greenhouse\u2019s energy balance. The energy content per photon depends on the wavelength; shorter wavelengths have a higher energy content per photon. For example, the energy content of a 400 nm photon (blue) is 1.75 times higher than that of a 700 nm photon (red). Joule and Watt are therefore units used to represent influences on the energy balance of the greenhouse and the plant.\n\n\n\n\n\n\t\t\t\t\t<\/p>\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\t\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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\n\t\t\t\t\t\tThe unit Joule is not suitable for determining the potential for photosynthesis. Plant photosynthesis is not related to the energy content of radiation but to the number of photons absorbed by chlorophyll. Therefore, the unit \u00b5mol\/m2\/s is used for the portion of light used by plants for photosynthesis (PAR light, 400-700 nm). \u00b5mol\/m2\/s is the unit used in horticulture to express the total available light (artificial and natural) for growth.\n\n\n\n\n\n\n\t\t\t\t\t<\/p>\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\t\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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\n\t\t\t\t\t\tUnits such as lumen and lux were originally developed for the human eye, not for plants. Since the human eye is most sensitive to green-yellow light, while plants absorb this part of the spectrum less efficiently, these units do not accurately reflect how plants use light for photosynthesis. For this reason, lumen and lux should be avoided in horticulture.\n\n\n\n\n\n\t\t\t\t\t<\/p>\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\t\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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\n\t\t\t\t\t\t\n\t\t\t\t\t\t\tUnit conversion\t\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/h3>\n\t\t\t\t\n\t\t\t\t\t\t\t\t\t

\n\t\t\t\t\t\tLight units can be converted into each other, but the conversion factor strongly depends on the spectrum of the light source. Note: conversion factors for different lamp types can vary significantly.\n\n\n\n\n\n\n\t\t\t\t\t<\/p>\n\t\t\t\t\n\t\t\t<\/div>\n\t\t\t\n\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Neem contact op met onze specialisten.\n<\/h2>\t\t\t\t<\/div>\n\t\t
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\n\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\tNeem contact met ons op<\/span>\n\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t
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Light – terminology When discussing light, various terms are commonly used, such as PAR, PPFD, and DLI. Below, we explain what they mean. Figure Sensitivity to light spectrum The sensitivity of plant photosynthesis to light of different wavelengths (left) and the sensitivity of the human eye to the light spectrum (right) PAR PAR stands for […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":410,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":""},"class_list":["post-412","page","type-page","status-publish","hentry"],"acf":[],"yoast_head":"\nLight-terminology - Agrolux<\/title>\n<meta name=\"description\" content=\"Light - terminology When discussing light, various terms are commonly used, such as PAR, PPFD, and DLI. Below, we explain what they mean. 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