Light plans have become an important tool in the LED lighting industry in recent years. When designing your grow space, the correct placement of light fixtures is vital for plant health and yield. Software programs now exist that allow manufacturers to make rough models that map levels of light intensity at different points in a room.
Light plans help assess whether a particular fixture will meet your needs given the layout of your greenhouse, grow room or grow tent. The technology is improving all the time, with more focus placed on light plans for horticultural purposes specifically. This means light plans can only be expected to become more accurate in the future, even if there are some current limitations worth knowing now.
Below, we’ll provide a guide of how light plans work and what to be aware of when reading a light map.
Light Plans: The Basics
To understand light plans, first let’s discuss how light mapping software actually works.
As light gets further away from a source, it gets spread out and diminishes. Light maps try to make an educated estimate about how much light intensity given parts of a room receive. The software works by factoring in the absolute intensity of a light source, the relative light intensity at a particular angle, and how much light reaches any given spot in a room.
This information is punched into an equation, which produces a map estimating intensity at various points in a room. More advanced software may also take into account factors such as reflected light and the presence of more than one fixture.
While light maps are not an exact science (more than that below), they can provide a good ballpark estimate when considering lighting for architectural or horticultural purposes.
Why Are Light Plans Important?
Most LED light fixtures list rough PPFD measurements, but this – in and of itself – doesn’t tell you much. PAR measurements directly under a fixture will naturally be higher than PAR measurements for plants on the side of the room, and most setups centralize their LEDs.
As you can see, without light plan, it is easy to fudge the value of a fixture. A light plan helps give buyers’ a more nuanced portrait of how their lights will work throughout a given setup. Rather than only relying on a center point measurement, a light map can show you how PPFD levels vary throughout rooms of different sizes.
As LEDs are a major investment, you always want to make sure a fixture is adequate for your setup. While you should take multiple factors into consideration – including a company’s reputation – reviewing light plans is integral to the buying journey.
Do Light Plans Have Limitations?
Even the best made light maps are not exact science given the multitude of factors that come into play in the average greenhouse or grow room. Light maps are still a useful tool for giving a fuller picture of a light’s capabilities, but there are a few limitations you should keep in mind when looking over a map.
Reflected Light
Good light mapping software does factor in reflected light, but this can get complicated fast. In a four-walled room, for example, the software needs to calculate how much light hits each wall from the fixture
and the amount of that reflected light goes on to hit a given spot in the room.
This adds
nine calculations: one calculation for the light coming directly from the fixture to the modeled spot, four calculations for the amount of light hitting the walls, and four more calculations for the reflected light reaching the modeled spot.
If you plan on adding objects to your grow room – which nearly all growers do – it gets even
more complicated as fans, air conditioners, and filtration systems
all reflect light as well.
This means getting
exact measurements can be complicated, but reputable providers usually do their due diligence. There may be a margin of error, however, so be sure to monitor and measure PPFD levels when using your lights as well.
Light Plans For Horticulture
Light-mapping software was originally designed for architectural purposes. It often models sample spots of a room every few feet, making ballpark estimates instead of exact measurements. The fact that measurements are inexact does not make a big difference when mapping with human comfort in mind; our eyes do not notice slight differences in light intensity. However, as any grower knows, even small fluctuations in light intensity can have a big impact on plant health and growth.
Light mapping software also measures in lumens and candelas per square meter, but what matters to plants is PAR and PPFD. Light mapping software therefore needs a correction factor to generate results, which is often dependent on the number and type of LED emitters used in a fixture. This can easily be manipulated by manufacturers to exaggerate the intensity of their lights. If a manufacturer is displaying
other common red flags, you may want to rethink a light map that seems too good to be true.
However, an otherwise reliable manufacturer is unlikely to manipulate a light plan. In most cases, light plans provide more detailed information, albeit in a slightly limited fashion.
The Bottom Line
Light plans are a very useful tool that can give you a more nuanced picture of light capabilities, allowing you to make the best purchasing decisions based on your needs. It is important to be aware light maps have
some limitations as every grower’s setup is different and some factors are difficult to account for.
As with any other factor, light maps should be viewed in conjunction with other information regarding your light fixtures. A good light map remains a vital part of the shopping process that provides you with more detailed information.
At California Lightworks, we use the most advanced light mapping software that incorporates the most cutting-edge fixture models to create some of the most accurate light maps on the market. If you have any questions about light maps or other matters, feel free to
reach out here. 
