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How to Read a Photometric Lighting Layout


When working on large exterior projects, sign lighting, or interior commercial lighting projects, having a photometric lighting layout is crucial, as it provides a wealth of information including fixture spacing, the number of fixtures needed, and the overall wattage consumption for a particular application. 

With such a large amount of information to sort through, it can sometimes be confusing to know how to read a photometric plan. Here’s a quick but handy guide when looking at a photometric layout to see how they work and the easiest way to read them.

Fixture Positioning

The first thing that is usually able to be seen is the direction and spacing between fixtures. By knowing where a specific fixture will face, you can ensure accurate readings and light output, and is particularly useful when a specific orientation is needed for a particular project.

Footcandle Readings and Calculations

Footcandles are the measurement of the strength of a particular light source on a surface. With photometric layouts, rows and columns of numbers can be seen, indicating the average footcandle reading at that point. These points add up to the average footcandle in an area to ensure the light is bright enough, and the average to minimum footcandle ratio to ensure lighting is even and consistent.

Heat Map

The heat map is simply a quick visual representation of the light spread of an area, using red for higher concentrations of light down to blue for a lack of light. This representation is extremely useful for determining even lighting and avoiding hotspots

Fixture Schedule

Lastly, the fixture schedule contains crucial product information for the fixtures used, including the wattage, voltage, lumen output, and number of a particular fixture type in an area.

For a photometric lighting layout on your next project, please feel free to fill out our Photometric Layout Form, give us a call at +1 (813) 649-8899, or email us at

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  • Michael Tomas