Why SAE J583 Matters For Your Fog Lights

SAE J583 is the Society of Automotive Engineers (SAE) designation of the fog beam pattern, it specifies a very wide beam with a flat horizontal cut off allowing minimal light above the horizontal cut off plane. This is critical in a fog application for multiple reasons, the first being the purpose of the fog light is to put the light beam low and wide so that the driver can find the edges of the road at low speed in poor weather without causing the beam to reflect light back at the driver in fog/rain/snow/dust, which reduces visibility in the conditions that the fog is primarily designed for.

The sharp horizontal cut off also allows this beam to be run in traffic without blinding other drivers, unlike any other auxiliary beam pattern. All other auxiliary patterns like wide cornering, driving, spot, flood, and diffused do not have the appropriate cut offs to be run on the street with oncoming traffic and should be considered for high beam use or off-road use only. While each of those other patterns serves a specific purpose, none of them will illuminate the edges of the roadway while providing a sharp cut off to prevent reflecting light back at the driver in inclement weather conditions, nor will they be safe to use in oncoming traffic, making any of them a poor choice for fog light use.

What an SAE J583 fog beam looks like

Fog pattern: Toyota Tacoma’s OEM TRD Pro Rigid LED fog pattern. Note the flat clean cut offs and wide beam of the SAE J583 pattern. This is what a fog beam should look like, the wide beam pattern illuminates the edges of the roadway while the sharp cut offs prevent light from reflecting back at the driver in inclement weather conditions and allows for the beam to be run on the street without blinding other drivers.

When looking for an aftermarket fog light, it is not uncommon for people to mistakenly select a light that is not actually a fog light and does not serve the same purpose. Often these lights are sold as aftermarket options for the OEM fog location, but just being in the bumper fog location does not make them a functional fog light. Below are a couple common pattern mistakes.

Spot pattern: Spot lights illuminate a very small area at high intensity designed to extend distance vision. The highly focused pattern does not have the spread to illuminate the shoulders of the roadway, and it does not have cut offs to prevent the blinding of oncoming traffic. It will be ineffective at helping the driver find the edge of the roadway in poor weather and is unsafe to oncoming drivers.


Wide cornering pattern (non-SAE): Wide cornering lights have the wide-angle projection as their name implies which will help illuminate the edges of the roadway, but they lack the proper cut off that is required for a compliant SAE fog light. Not only does the lack of cut off make them extremely hazardous to other traffic, it also reduces their effectiveness in poor weather conditions like fog.

The ideal fog light will have a high-intensity beam pattern with a wide horizontal angle of projection to illuminate the shoulder and provide a sharp gradient cut off to minimize light spill above the horizontal cut off plane. Most OEM fog lights are far from an ideal fog light, they often have poor pattern intensity and even worse gradient cut offs, meaning they are not very effective at putting light on the road at the shoulder where you need it and put too much light above the horizon where you don’t.

This is what oncoming drivers see with a wide cornering pattern. Rigid SAE J583 D-Series left vs wide cornering right.

While many brands may offer a single SAE fog light, Rigid provides an entire product line of SAE J583 fog lights and to help further enhance poor weather performance, most of the fog lights are also available in selective yellow. The Rigid fog optics provide tight gradient cut offs making it possible to not only significantly increase the light output intensity overstock, but also decrease the light spill above the horizon compared to most OEM fog lights.

This SAE street legal pattern makes the light more effective for the driver in poor weather conditions while minimizing the glare exposed to oncoming drivers compared to most stock fog lights. Rigid’s SAE D-Series lights are well known as the industry benchmark for an SAE fog pod due to their high-intensity output and sharp cut offs. Rigid offers a wide variety of other SAE J583 fog lights of various shapes and sizes to best fit the light to the needed application.

Having personally tested dozens of replacement SAE fogs, I am often asked what fogs I run on my own personal truck. After extensive product testing and comparisons, I run Rigid SAE D-Series in selective yellow.

Article Sources

About the author

Ryland Wallace

Ryland has a degree in Vehicle Design and is an extreme lighting enthusiast. He has been modifying vehicles since his first car at 16 and likes data-backed analysis on everything possible.
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