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Lighting Plans and Photometric Analysis

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What is a Photometric Analysis?

A Photometric Analysis, or also known as a Lighting Plan shows how a lighting solution would look in a project or given area.

Modeling an indoor or outdoor area lighting layout is possible using photometric software.  By importing existing layouts and CAD designs it enables the end user to see how the project would look in their given space.

Different fixtures can be used at specific locations, angles, orientation and height by the lighting engineers.

A comprehensive visual layout report gives the optimal calculated lighting levels. The report displays calculation points showing the foot candle reading for each point in the project.

How do You Read a Photometric Plan?

There is a lot of information to go over after you get a The Lighting Center photometric plan. It’s essential you understand the information to get the most out of the plan. 

Indoor Basketball Court Lighting Calculation

Fixture Used

150W LED UFO High Bay

(24 fixtures)

1. The Foot Candles

Look on the plan above. There are data points inside the basketball court that represent the foot candle readings calculated at each specific point.  Either foot candles or lux can be calculated for the report.


2. The Fixture Locations

In this example, the red dots represent the location of the fixtures giving you a clear indication of where the lights are in the plan.


3. The Schedule Details

Located at the left bottom side on this plan is the schedule.  Details about the fixtures used in the plan are shown here. If more than one fixture type is used, it would be shown here in this section.


4. The Calculation Area

The Calculation Area just to the right of the schedule shows distribution ratios and light levels . The average foot candles in the defined space is of note here. Next it shows the maximum and minimum calculated foot candle for the plan. The average is the most important, it is the target foot candle reading for the plan. 

The next two readings are also important. The Avg/Min ratio is the average foot candle to the minimum calculated point with the best this number can ever be is 1.  Next is the Max/Min ratio which is the ratio of the brightest point to the one with least light. Again, the best this number can be is 1. It’s almost always a higher number than the Avg/Min ratio.

Shooting for an avg/min ratio between 2 and 3 is ideal. The higher the number is the more spotty your lighting will be on your plan. It’s important here that a well defined calculation zone needs to be achieved. Looking at the above example, if the calculation zone included an area outside the court, the avg/min ratio would rise only because min levels would drop.

Developing a good photometric light analysis depends greatly on understanding the area. 

How Do I Avoid Light and Spotty Distribution Issues?

We hear this scenario alot and it’s a big problem in the lighting industry. Facilities want to convert over to LED lighting, so they go to a large online retailer’s website.  They look for and compare the products, and finally choose making their best educated guess at what lighting product they should install.  And after it’s installed… Now comes the painful discovery.

The light is way too bright!

The light isn’t bright enough!

There’s a huge glare!

The lighting  is spotty and not consistent!

The lighting is bright under the fixture, but dark in the other areas!

How were you supposed to know what the lighting was going to be like?

The light appeared to be exactly what you needed and lights are basically the same, right?

Choosing the right LED lighting can be a bit more technical than choosing the cheapest online fixture. You need a full understanding of the lumens, foot candles and beam angles.  This will determine the best lighting solution for your project.

But you’re not a lighting engineer.

So how are you supposed to know all this?

Easy! You’re not! That’s exactly why we show you the results BEFORE you purchase. It takes the risk out of buying lights.

The problem with purchasing lights off the shelf from large e-commerce sites is you have no idea what you’re getting. Manufacturers sometimes get rid of old inventory on these sites. Lights with old chip sets and crazy beam angles. It looks like a good price, until you install them and discover you’ve made a big, costly error.


Light levels and distribution can vary greatly between what appears to be 2 comparable fixtures (especially when looking only on fixture watts). Take out the risk of purchasing old “end of life product” by getting a photometric done. We do these for free!  Unlike, our large e-commerce sites that charge hundreds of dollars for these reports or won’t even do it.

How To Understand Light Brightness

Introducing the concept of foot candles or lux helps us understand light levels.  Basically they’re the same, a term to measure light. Readings can be taken using a light meter or a light meter app on a smartphone. A dedicated light meter give better results; but it’s ok to use a free light meter app to get a basic understanding of the light in your location.

Let’s say you have a facility that you are looking to upgrade to LED Workshop Lights. A good way to go is to get a light meter app on your phone. Take several readings within your facility to get a better idea of your needs. Make sure you go underneath lights, in between and in the center of the space. Include the edges, in your readings as well.

From your readouts, you’ll get a good idea of your lighting performance, and the current light levels.

You can also asses:

Are my light levels too bright or too dim?

Are my light levels uniform and evenly distributed?

Where is improvement necessary looking at the current light levels?

Understanding Lighting Basics


1. What is a foot-candle?

A foot candle is the amount of light measured in a specific location.  The light can be from one or all lights contributing to the specific reading for that location. Foot candles, or LUX,  is the prefered measurement for describing a light level for a project, facility or location.


2. What are lumens?

Lumens are the amount of calculated light that a bulb or fixture produces.  This unit of light is useless by itself.  When it becomes useful is when it measures the collective lumens produced by a fixture or bulb.


3. What is a Beam Angle?

A fixture produces light and how its focused requires optics, or no optics. For example, lights mounted high up need optics to focus the light in the direction its needed (towards the ground, for example). However, adding a tight optic to a light and mounting it at a low height will result in spotty lighting.  Areas will have intense bright spots with dim areas in between the lights.

Poor lighting results from not having the right amount of lumens and improper beam angles. Its important to understand your required foot candles. Then you can choose the correct fixture with the perfect amount of lumens and with optimum beam angle.


What is a photometric plan?

A Photometric Lighting Analysis is a way to view a proposed lighting solution over a given area. Using photometric software, you can model an indoor or outdoor room or area layout. The software can also import existing layouts and CAD designs. Lighting engineers can input fixtures at specific locations, angles, orientation and height. The software calculates light levels and provides a comprehensive visual layout report. The report displays calculation points representing the foot candle reading at that location.

How do you do Photometrics?

Photometrics are done by using software specifically designed to create lighting plans. The software allows you to define specific indoor or outdoor spaces, import light fixtures, and then place these light fixtures on the model. The software then calculates the amount of light at specific points in the model along with how well the light is distributed.

How do you read a lighting plan?

A light plan will show you a model of your area and the location of the fixtures. It then has points in the model that shows you foot candle readings at that point. Also included in the model are average, maximum and minimum foot candle readings. Also included is distribution levels – a definition of how well the light is distributed within the model. A good design will have avg/max distribution levels under 3.0.

Photometrics  Plans – Large and Small

Photometric studies are done on indoor and outdoor locations from large and small facilities alike.  Light studies are a must for warehouses, parking lots, baseball fields, school gymnasiums and office locations. They are easily created from your CAD files for indoor projects or outdoor locations using google maps.


An Indoor Factory Photometric Study

In this case study, the current lighting was around 12 foot candles throughout the factory. They contacted TheLightingCenter wanting to upgrade to LED.  Like most large customers, they wanted to do it right and perform a light analysis first. Their goal for upgrading to LED was to get more light, save energy, and stop the unnecessary occurance of changing out bulbs and ballasts.

The customer gave TheLightingCenter  a CAD file (.dwg file) for us to import into our software. We took one area to model what the project would look like by replacing their HID lighting with a combination of 120 Watt and 200 Watt LED High Bays. For this model in the main work area, we increased foot candles from 12 to 41 with an Average Minimum Ratio of 2.31 indicating uniform lighting levels through out.

Being able to model this project for the customer let’s them to see the incredible results. All before spending any money.

Fixture Used

200W LED UFO High Bay

(39 fixtures)

Fixture Used

120W LED UFO High Bay

(4 fixtures)

Photometric Study For Outdoor Street Lighting

In this example of a DOT application, we replaced 1500W High Pressure Sodium lights to 600W LED High Mast Area Lights with 150 degree optics. The ISO-lines show foot candle transitions, with the red line highlighting 0.6 foot candles.

Photometric studies show the customers how the lights perform before having to buy. It allows for the lights, lumens, and optics to be adjusted to meet the desired specifications.

TheLightingCenter used images from google maps to create an outdoor photometric plan for the DOT.

Fixture Used

570W LED DOT High Mast (10 fixtures)

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Last Updated: 12/08/2020

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