Horticulture Lighting Metrics: Understand LED Grow Lights What It All Means

Understanding LED Grow Lights: Horticultural Lighting Metrics

Today’s grow lights are more cutting-edge than ever. With that, there’s plenty to grasp, especially concerning LED grow light metric or metrics and the wealth of information surrounding them. Horticulture lighting metrics are all-important when cultivating plants indoors. The same applies to crops ranging from cannabis to culinary herbs and microgreens.

At first glance, grow light PAR figures and so-called photosynthetic photon efficiency readings can seem mind-boggling. However, that needn’t be the case. To demonstrate, the following is a closer look at several crucial horticultural lighting metrics. These metrics include PAR, PPF, PPFD, and more.

Horticulture Lighting Metrics

Perhaps the best place to start surrounding horticultural lighting metrics is with PAR. PAR is among the most commonly used plant cultivation grow light metric figures. But understanding this one metric is often for nothing if growers don’t also understand the likes of PPF and PPFD.

It can be a confusing topic. However, there’s considerable overlap between several of the most common metrics, including grow light photosynthetic active radiation values and more commonly discussed lumens, lux, or luminous flux. The same is true of photosynthetic photon flux and photosynthetic photon flux density – two more advanced grow light metrics.

As such, understanding one metric often serves as the basis for gaining knowledge of one or more other vital metrics from the horticultural lighting spectrum. Many people choose to begin by studying grow light PAR or photosynthetic active radiation – one metric that’s in widespread use across all types of lighting worldwide and has been for decades.

Grow Light PAR Photosynthetic Active Radiation

Interpreting the various horticultural lighting metrics used today is invariably best approached with a deeper initial understanding of PAR. High PAR grow light fixtures have been central to indoor plant cultivation for many years. Today, high PAR LED grow lights are almost universally the serious grower’s lighting fixture of choice.

PAR stands for photosynthetically active radiation. PAR most commonly measures a specific region in the middle portion of the lighting spectrum, ranging from 400 to 700 nanometers. Nanometers or nm readings define the perceived color of transmitted light.

Red light exists in the mid-600s, green in the mid-500s, and blue or violet in the low- to mid-400s. The human eye is most sensitive to green light bearing a slight yellow hue in the middle of the PAR spectrum. Yet, most plants respond best to light in the blue or violet and far-red spectrums at either end of the scale.

PAR is often confused with lumens. However, lumens—or lux—represent the metric that human eyes can see versus the photosynthetic active radiation or PAR used or “seen” by plants to photosynthesize. The lumen outputs of LED grow lights tend to track parallel to their PAR figures.

Lumens, Lux, or Luminous Flux

As we’ve already learned, people and plants don’t “see” light the same way. For example, we perceive green-colored light as the brightest and most important. By contrast, plants primarily utilize red and blue light.

As a rule, lumens, lux, or luminous flux figures are for our benefit. That’s as opposed to being used as a primary metric alongside the likes of PAR or photosynthetic active radiation. As such, PAR, PPF, and PPFD are far more crucial metrics for plant cultivation.

Lumens, lux, or luminous flux figures are calculated using the human eye’s sensitivity to particular wavelengths as their basis, not the benefit of these wavelengths on plants and their growth. A high-lumen light, therefore, may not make the best grow light because of this. That’s why focusing on grow light PPF, PAR, PPE, and PPFD instead is always more advisable.

Whether in terms of LED grow light PAR or adequate LED grow lights lumens, for beginners especially, one of the best ways to ensure the correct horticultural lighting metrics is with what’s known as a full-spectrum grow light.

Read more: Some Secrets Behind Full-Spectrum LED Grow Lights

PPF Photosynthetic Photon Flux

PPF grow light figures can vary wildly. Therefore, ensuring optimal output should be central to any grow light buying decision. PPF stands for photosynthetic photon flux. Like PAR and lumens, PPF or photosynthetic photon flux figures tend to track parallel to photosynthetic active radiation or PAR readings.

Photosynthetic photon flux measures the total light output expressed via photosynthetic active radiation or PAR readings on a second-by-second basis. Whereas PAR is measured in nanometers, PPF is expressed in so-called micromoles of photons per second – most commonly displayed as µmol/s.

These figures determine how efficient a grow light is at converting electricity into the all-important photosynthetic active radiation reflected in the aforementioned PAR readings. While PAR is easily read with straightforward equipment, taking PPF readings is much more specialized. As such, photosynthetic photon flux is typically only determined in dedicated light laboratories.

Because of this, when choosing an LED grow light, for example, based on PPF requirements, it’s vital to do so from a trustworthy manufacturer. That’s one invested in the laboratory testing required to achieve accurate photosynthetic photon flux figures that growers can use to ensure optimum plant growth and impressive subsequent crop yields.

PPFD Photosynthetic Photon Flux Density

An appropriately rated PPFD grow light is a must when growing plants indoors. Regardless of the scale of operations and whether raising plants in single figures or on an industrial level, it’s vital to ensure that photosynthetic photon flux density is correctly accounted for. LED grow light PPFD figures should be available from all respected grow light manufacturers.

Photosynthetic photon flux density is slightly easier to measure than the photosynthetic photon flux discussed above. That’s because, in the simplest terms, photosynthetic photon flux density or PPFD concerns the level of light falling on a given surface rather than the measurable radiation level output by a lighting unit on a second-by-second basis.

At the same time, PPFD is still measured in seconds – this time expressed as µmol/m2/s. Such µmol/m2/s readings reflect micromoles of photons per square meter per second. Although easier to gain a base PPFD measurement than a base PPF measurement, achieving an accurate photosynthetic photon flux density reading still requires specialist equipment, namely a spectrometer.

Spectrometers measure photons emitted by light sources such as LED grow lights. However, basic PPFD or photosynthetic photon flux density readings can also be taken with more readily available PAR light meters. As the name suggests, these are more commonly used to measure PAR or photosynthetically active radiation by hobbyist growers and more serious operators alike.

PPE Photosynthetic Photon Efficiency

And last but certainly not least, PPE or photosynthetic photon efficiency. In addition to selecting a high PPFD LED grow light or lights, growers must also understand and appreciate their plants’ PPE or photosynthetic photon efficiency requirements. PPE or photosynthetic photon efficiency is an expression of the photon output by fixtures such as LED grow lights.

Photosynthetic photon efficiency—or PPE—is measured using the same metric as PPF or photosynthetic photon flux. That’s micromoles of photons per second or µmol/s. However, unlike when determining PPF figures, the same µmol/s reading is divided by the wattage of a given light source to achieve an accurate PPE measurement.

The resulting figure represents the PPF output for that fixture – a fraction of its PPF or photosynthetic photon flux reading. As with photosynthetic photon flux measurements, determining accompanying photosynthetic photon efficiency figures is similarly tricky by virtue of also requiring a dedicated light laboratory to achieve a preliminary reading.

Achieving Accurate Horticultural Lighting Metrics

Given the difficulty of achieving a full complement of accurate horticultural lighting metric figures, it’s invariably best to choose a manufacturer who can report accurate, independently measured PAR, PPF, PPFD, and PPE figures.

When buying one or more LED or other grow lights, ensure the relevant manufacturer can provide complete information about their products’ efficacy, output, spectral quality, and more. This information should feature on any respected manufacturer’s product specification sheets.

Alternatively, serious growers can acquire a spectrometer or a more readily available PAR light meter. However, to achieve accurate readings for trickier metrics like photosynthetic photon efficiency or photosynthetic photon flux, it will invariably be necessary to call for the help of a specialist laboratory.

Calling in such outside help will often prove prohibitively costly for all but the largest-scale growers. Hence, the utmost importance of working with a trusted and reliable grow light manufacturer with up-to-date product specification sheets from the outset.

Furthermore, aside from horticultural lighting metrics, ensuring the best crop growth and maximized yields also requires an additional deeper understanding of the ideal LED grow light setup, including precisely what’s needed and how to get started.

Read more: Determining The Ideal LED Grow Light Setup: What & How?

Horticulture Lighting from Bata

Appropriate PAR, PPF, PPFD, and PPE metrics give growers on all scales the assurances needed to ensure a return on their investment or investments into their all-important lighting setups. That’s why choosing an established grow light manufacturer is so important. One such manufacturer is Bata.

Bata, headquartered in Guangdong Province in southeast China on the border with Hong Kong and Macau, is a global leader in LED-powered horticultural lighting. The result of many years of intensive study, the company is a high-tech enterprise with extensive in-house product development, manufacturing, and research facilities.

Bata now produces over 100 unique LED grow light products, each backed by exceptional and highly dedicated ongoing customer support. In 2023 and beyond, Bata is wholly committed to continued innovation within LED horticultural lighting.

The company also maintains an overarching vision for growers worldwide, promising improved productivity and more intelligent crop growth today and for years to come. To learn more about Bata and how the company is developing lifelong relationships with clients worldwide, visit BataGrowLight.com, email info@batagrowlight.com.