Photometric Plan

Technical Lighting Plan Terms You Should Know

One of the biggest challenges of buying new lighting or upgrading to LED lighting from existing fixtures is anticipating how your new lights will look and function in your space. Luckily, there is a solution.

A Photometric Lighting Plan is a software report of LED Lights placed within an indoor or outdoor area. Using a special lighting software program, you can create a simulation of an indoor room or an outdoor area. The software is capable of importing layouts, CAD diagrams, and even scaled Google maps of outdoor areas, particularly interesting when creating lighting plans for outdoor sports facilities.

The software can place the fixtures inside the plan at specific locations and heights, taking into account the ceiling height, which is crucial for proper light distribution. Lighting specialists use the software to analyze the calculation surface, which displays light distribution and zone-specific statistics. They also consider the type of light sources and light source specifications to ensure optimal performance and compliance with lighting requirements. The fixtures can be oriented and aimed. The lighting plan calculates foot-candle light levels, shows how balanced the light is, and provides a comprehensive printable PDF report.

Lighting Terms

Lumen: A lumen is a unit of light. By itself, it’s useless, but it becomes useful when it defines the collective lumens produced by 1 fixture or bulb. It is the amount of visible light that a fixture emits.

Foot Candle: A foot-candle is a measurement of light at a specific location, and many lights can contribute to the specific foot-candle reading at that location. Foot candles (or its equivalent LUX) are the requirement that most are looking for when they describe a light level for a project, facility, or location. Standards set by the Illuminating Engineering Society (IES) guide proper lighting levels, ensuring safety and uniformity in lighting design.

Photometric Study Report: A photometric study report is a detailed document, typically 5 to 20 pages, containing graphs, charts, and analysis that summarize the results of a lighting or photometric analysis. It follows IES guidelines and helps interpret lighting performance for a given space.

Ambient Lighting: Ambient lighting refers to the overall illumination within a space, providing comfortable and functional light levels for general activities and creating a welcoming environment.

Accent Lighting: Accent lighting is used to highlight specific areas or objects, such as products in a retail setting, enhancing visual appeal and drawing attention without overwhelming the space.

Beam Angle: The beam angle of a lamp is the angle at which the light is distributed or emitted. This can be done with additional optics, or as is the case with LEDs, by engineering the light in a specific way. LEDs have an extremely large range of available beam angles.

How to Read a Photometric Plan?

A lighting plan won’t provide you with any benefit unless you know how to read it.

A photometric plan serves as a guide by presenting photometric data and key data points for analysis. These data points include important measurements such as uniformity and foot-candle levels, which are essential for evaluating lighting layouts.

If this is your first LED Lighting Supply photometric plan, it may seem like a bunch of complex figures and statistics. However, it isn’t as difficult to understand as you might think.

Refer to the lighting plan for the basketball gymnasium on the right as we share some terms to familiarize yourself with how these plans work. There are 4 main parts of every lighting plan.

1. Foot Candle Measurements

A foot-candle represents the amount of light that reaches a surface area, and it’s measured in lumens per square foot. In the above plan, you’ll see that there are several reading points within the lighting plan. These represent the foot-candle readings for each specific point. The average rating and calculation zone's statistics are used to assess lighting uniformity, helping to determine how the brightest point differs from the least bright point, which is important for visual comfort and compliance. And if you’d rather look at the layout in meters, the software can also calculate lux instead of foot-candles.

2. The Fixtures

The light fixtures, arguably the most important element in a photometric lighting plan, are represented by red dots. In outdoor environments such as parking lots, it is crucial to properly place light poles and use listed fixtures to ensure optimal lighting coverage, safety, and compliance with regulations.

The dots indicate the optimal locations for the light fixtures to achieve the best lighting coverage.

Fixtures can be swapped out and plans recalculated to find ideal lighting for specific environments and areas, including parking lot applications and other large outdoor parking lots.

3. The Schedule

This is an extremely important part of a lighting plan that is often overlooked. The schedule is found at the bottom left of your lighting plan, and it goes into further detail about the types of fixtures recommended in the lighting plan.

The schedule helps you select the right fixtures by considering factors such as shape, size, and beam angle, and ensures that the lighting solutions provided are tailored to meet the specific needs of your project.

4. The Calculation

This is where some of the most valuable information in the lighting plan is found. This section is found on the right of the schedule and identifies the light levels and distribution ratios of the fixtures outlined in the schedule. It provides some useful information about the foot candle measurements in the plan, including the average, maximum, and minimum. These numbers are often used to ensure that projects are in accordance with building codes.

Out of these numbers, the average is the most significant. This is the ideal or “target” foot-candle reading for the entire project. We can then calculate an Average/Minimum foot-candle reading, which shows us how much the dimmest spot differs from the average.

The Max/Min ratio is also important, as it shows the overall lighting distribution for the space. Building codes are made so that buildings have an even distribution, which helps with visual comfort and safety. Photometric analysis using these ratios helps identify dark spots and ensures uniform lighting, which enhances visual comfort and prevents areas of insufficient illumination.

Lighting Plan Considerations

Inadequate Light Levels or Spotty Distribution

Bad distribution and poor lighting levels are a major issue in the lighting industry. Many facility managers who are looking to convert to LED lighting end up buying products online without going through a proper analysis. They make assumptions about what should work in their space, and encounter problems once they have bought and installed the new lighting. We end up hearing the following complaints often:

• It’s too bright.
• It’s not bright enough.
• The light is not uniform.
• The light is too bright beneath the fixture.

Consulting lighting specialists is essential to ensure proper lighting levels and that all areas are well lit, which helps prevent these common issues.

This is why we always suggest a photometric lighting plan. Otherwise, there is no sure way to know what your outcome will be. Even though some suppliers will suggest that many fixtures aren’t all that different from each other, we know that couldn’t be farther from the truth.

The only way to accurately predict how your lights will look is to have an in-depth understanding of how light behaves in large spaces. But unless you are a lighting engineer, this information is out of your wheelhouse. And that’s where the photometric lighting plan comes in. A photometric lighting plan takes everything into account and does the math for you so that you can make an informed lighting purchase, whether or not you’re a lighting engineer.

The issue with buying lighting fixtures online is that you can’t be 100% sure of what you are buying. A lot of the time, manufacturers will sell old inventory with outdated features and old chipsets. It may seem like a bargain, but you’ll quickly realize that you’ve made a huge mistake.

Understanding Your Current Light Levels

You can’t understand where you’re going if you don’t understand where you’ve been. Alright, that’s not exactly how the saying goes, but it does still apply here. To understand light levels, let’s introduce the concept of foot candles or lux. They are the same thing: light measurements.

You can take light readings using a handheld light meter or an app on your smartphone. A free light meter app gives some reliable basic readings, but if you have a complex light environment or want to be completely sure, we recommend investing in a light meter.

For example, you may have a production facility and are looking to upgrade to LED Shop Lights. A good process would be to install a light meter app on your phone and use it to take several readings around your facility. Go under a light, go between lights, go into the center of the space, go to the edge, and take readings.

These measurements can be analyzed by calculating the surface and calculation zone, and are often expressed per square meter to ensure accurate assessment of illumination levels and compliance with lighting standards.

From this, you will get a good idea of how your current lighting is performing and your current light levels. But you can also use this method to determine things like:

• Are my light levels OK, too bright, or too dim?
• Are my light levels pretty uniform and evenly distributed?
• Would I like to improve the light levels, or are things OK?