Vertical and Horizontal Illuminance: Light Intensity Measurement

In lighting design, light intensity measurement is crucial for ensuring optimal illumination in various environments. Luminous flux, which measures the quantity of light emitted by a source, plays a significant role in calculating illuminance levels and determining the number of luminaires needed for desired lighting standards. Measuring light intensity involves quantifying the amount of light, or luminous intensity, that reaches a surface, which is essential for applications ranging from sports facilities to commercial spaces. This article explores key aspects of light intensity measurement, focusing on the importance of vertical and horizontal illuminances, how illuminance is measured, and the role of photometric studies in predicting lighting performance.

Understanding Light Intensity Measurements

Depending on the type and level of play of your specific application, the required light intensity measurement will differ. Illuminance, also known as incident light or brightness, refers to the amount of light that hits a surface. The only way to be sure that proper light levels are available is to measure them. Calculated by the density of lumens per unit area, illuminance is a measure calculated at a surface (like the clay of a tennis court). The standard measures for illuminance are footcandles and lux.

Light should be measured on both the horizontal and vertical planes. The horizontal plane is critical for calculating horizontal illuminance, which is the amount of light that lands on a horizontal surface, such as a tabletop. This measurement is significant as it helps in determining the observation angle and the vertical angle of light reflected, which is essential for better illumination analysis. The vertical measurement is known as the vertical illuminance and is the amount of light that lands on a vertical surface, such as a wall. It is important to consider both vertical and horizontal illuminances in your lighting design.

How Is Illuminance Measured?

In the United States, horizontal and vertical illuminances are measured in footcandles; most other countries measure this luminous emittance in lux. Footcandles and lux are quite similar; one lux equals one lumen per square meter. If you have a lux light intensity measurement, simply divide it by 10.76 to solve for footcandles. Conversely, if you have a footcandle measurement, multiply it by 10.76 to solve for lux.

What Happens When Vertical Illuminance Is Not Factored Into a Design?

Measuring illuminance to achieve satisfactory results ensures minimal shadowing. Illuminance values for applications and lighting solutions typically depend on the complexity of the visual tasks being performed for the lighting setup. For instance, if a tennis court is illuminated from only one side or end of the court, it could very well have sufficient horizontal footcandles but may lack the desired vertical footcandles. Any person, piece of equipment, or even a tennis ball, would create a shadow and would seriously affect one’s ability to play. Measuring both horizontal and vertical illuminances will help even out the light and minimize shadowing.

Does Symmetrical Lighting Guarantee Sufficient Light Levels?

While it is unlikely that anybody would design lighting for a sports area or a facility from only one side, lighting specialists at Access Fixtures frequently get requests for this kind of design. If a sports area, driveway, stadium or other large outdoor area is illuminated with a symmetrical lighting arrangement, many tend to assume the vertical illuminance will be sufficient and balanced. Unfortunately, that is not always correct.

For instance, if a balanced and symmetrical lighting design causes light trespass near the property line, the fixtures causing that light trespass might have to be redirected, shielded, or replaced with lower-wattage units. The fixtures on the other side of the court, however, may be fine as they are. After making these adjustments, the design will no longer be symmetrical and its vertical illuminance will be far less even. There is even the possibility that the resulting vertical illuminance will be insufficient for that specific court or facility. Vertical illuminance must be measured in asymmetrical lighting designs.

Photometric Studies Predict Vertical and Horizontal Illuminance

Photometric studies, also known as photometric analyses, are the easiest way to calculate horizontal and vertical illuminance before a project is built. Photometric studies are computerized simulations of lighting plans. The results of a photometric study will predict the horizontal illuminance and vertical illuminance at multiple points of the area being simulated. To order a photometric analysis, click here.

Speak to an Access Fixtures Lighting Specialist about Vertical and Horizontal Illuminances

Are you in the market for a new fixture? Not sure how many lumens your space needs? Call the lighting specialists at Access Fixtures today! We want to make sure you get the exact fixture for your needs, your budget, and your goals. We are passionate about lighting and love what we do—we’ll get you an answer. Contact us at 800-468-9925.

Conclusion

Understanding and accurately measuring light intensity, including both vertical and horizontal illuminances, is fundamental to creating effective lighting designs. Whether for sports facilities, commercial spaces, or outdoor areas, using tools like light meters and photometric analyses can ensure optimal lighting conditions that enhance safety and performance.

Vertical and Horizontal Illuminance Frequently Asked Questions

You have Light Intensity Measurement questions. We have answers. If you have a question that isn’t answered below, contact an Access Fixtures lighting specialist at (800) 468-9925 or click here to visit our customer service page.

What is illuminance in lighting?

Illuminance is the measure of the amount of light falling on a surface, typically measured in lux or footcandles. It is a critical aspect of lighting design, as it determines how well an area is illuminated and affects visibility and comfort.

How is light intensity measured?

Light intensity is measured using a light meter, which quantifies the luminous intensity in units like lux or footcandles. This measurement helps ensure that lighting meets the required standards for various applications.

What are the differences between lux and footcandles?

Lux and footcandles are units of measurement for illuminance; 1 lux equals 1 lumen per square meter, and 1 footcandle equals 10.76 lux. While lux is commonly used internationally, footcandles are often used in the United States.

Why are vertical and horizontal illuminances important?

Vertical and horizontal illuminances are crucial for achieving balanced lighting, reducing shadows, and enhancing visibility. This is especially important in areas like sports facilities and commercial spaces, where proper lighting is essential for safety and functionality.

What tools are used for measuring light intensity?

Light meters are commonly used to measure light intensity, providing readings in lux or footcandles. These devices are essential for accurately assessing the lighting levels in various environments.

How does photometric analysis help in lighting design?

The photometric analysis predicts how light will behave in a space, aiding in the design of efficient and effective lighting systems. This analysis uses simulations to evaluate the distribution and intensity of light, ensuring optimal lighting conditions.

What is a light meter?

A light meter is a device used to measure the intensity of light, crucial for determining the illuminance of a space. It provides accurate readings that help in designing and adjusting lighting systems.

What happens if vertical illuminance is not properly measured?

Inadequate vertical illuminance can lead to shadowing and poor visibility, affecting the functionality of the space. It is important to measure both vertical and horizontal illuminances to ensure a well-lit environment.

Can symmetrical lighting designs ensure proper illuminance?

Symmetrical lighting designs do not always guarantee adequate illuminance, especially if adjustments are needed to address issues like light trespass. It is important to measure and adjust lighting to ensure proper distribution and intensity.

Why is it important to measure both vertical and horizontal illuminances?

Measuring both vertical and horizontal illuminances provides a comprehensive understanding of how light interacts with different surfaces. This is crucial for creating balanced lighting environments that enhance visibility and safety.