How to Measure Light

July 21, 2016

How do you ascertain the illumination level needed for various applications so as to achieve optimal light and safety as well as visual comfort? We often install light bulbs according to their watt consumption without knowing the amount of light they project. How do we measure light? In the lighting industry, we often speak of foot-candles, lumens, and lux. The following are basic references that will help you measure light.

Here is a simple illustration that will help you understand the foot-candle measurement. Imagine setting a candle at a distance of 0.30 meters (1 foot) from a flat wall on which we’ve drawn a square shape measuring 0.09 square meters (1 square foot). One lumen per square foot will illuminate this surface.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Foot-candle is the most widespread lighting measurement in the industry. Why do we still use the word “candle” to measure light in this day and age? The explanation for this choice dates back to origins of the candle itself. When people began to measure the intensity of light, candles were the most common light source available.

At that time, the candle-making industry provided a consistent, steady, clean, and efficient way to measure light; thus, the reason for this well-known expression, even today.

Lumen and lux

The lumen is a significant entity: it measures the total amount of visible light emitted by a given source. All other measurements are based on the lumen.

The lumen measurement originated from the basic concept of foot-candles; it might be illustrated, more or less, by the image shown here. A more scientific definition exists today, but this drawing helps visualize the lumen.

Picture a candle set in the middle of a sphere measuring 0.60 meters (2 feet) in diameter; when we cut a hole that measures 0.09 square metres (1 square foot) in the centre of this sphere, the light that shines through is what we define as a lumen.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

A foot-candle equals one lumen per square foot; this is a British measurement. Using the metric system, a lumen is measured by square meter, or a lux. Thus a foot-candle is equivalent to approximately 10 lux or 10.57 lux.

A higher number of lumens are indicative of a brighter, more intense light, whereas a lower number of lumens represent dimmer, more subdued lighting.

How to measure a lumen or a lux

In reality, lumens are quite difficult to measure: laboratory tests are usually required. Consequently, if you want to know the number of lumens projected by your lamp or fixture with integrated bulb, you may want to refer to the product packaging or consult the luminaire catalogue.

Transition from watts to lumens

It does make any sense to evaluate the amount light according to the watt consumption of the lamp. When you want to replace a light bulb, follow this simple rule of thumb to convert watts to lumens, and vice versa.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

How much lighting do you need?

Ordinarily, we establish the optimal lighting requirements based on the need for appropriate foot-candles. How can you determine the best amount of lighting for your particular application? The Illuminating Engineering Society of North America (IES) has set a number of guidelines that you may wish to consult.

The following is an infographic that sets out a number of guidelines to determine the amount of lumens you need to light the various rooms of your house.

 

 

 

 

 

 

 

 

 

 

 

 


This article was first published by Standard in its online journal, www.standardpro.com/category/our-online-journal/. Journal articles give tips and advice on how to improve your environment through a better lighting solution, whether it’s in your office, warehouse, home, stores, or on the road…

Related Articles


Latest Articles

  • A Career with Purpose – Apprentices Building Canada’s Reduced Carbon Future

    A Career with Purpose – Apprentices Building Canada’s Reduced Carbon Future

    January 27, 2023 By Yoana Turnin, Project Manager, EHRC In 2021, Canada joined 120+ other countries in committing to achieving net-zero emissions by year 2050 in an effort to “avert the worst impacts of climate change.” In a few words, that means either reducing or offsetting the economy’s greenhouse gas emissions through electrification, energy efficiency… Read More…

  • Challenges, Opportunity, and Labour Demand in the Construction Industry

    Challenges, Opportunity, and Labour Demand in the Construction Industry

    January 27, 2023 By Blake Marchand There is some uncertainty in the overall market right now, relating to inflation, interest rates, even global events like the war in Ukraine has an impact. These factors will have an impact on the construction industry, which may have an impact on broader opportunities for electrical contractors. Although, anecdotally… Read More…

  • First Retrofit Financed by the Canada Infrastructure Bank Receives IREE Certification

    First Retrofit Financed by the Canada Infrastructure Bank Receives IREE Certification

    January 27, 2023 The Canada Green Building Council (CAGBC) and the Canada Infrastructure Bank (CIB) have announced Dream’s 366 Bay St. redevelopment in Toronto is the first retrofit project financed by the CIB to achieve Investor Ready Energy Efficiency (IREE) certification. IREE certification is part of the CIB’s Building Retrofits Initiative and is administered through… Read More…

  • Natural Resources Canada Launches Call for Proposals for the Delivery of the Codes Acceleration Fund

    Natural Resources Canada Launches Call for Proposals for the Delivery of the Codes Acceleration Fund

    January 27, 2023 The Government of Canada is taking action to fight climate change by reducing greenhouse gas emissions and improving energy efficiency. The buildings sector is the third-largest source of emissions in Canada, which is why Canada’s upcoming Green Buildings Strategy will be critical to achieving Canada’s climate targets, creating more climate-resilient buildings and supporting jobs in many sectors across the… Read More…


Changing Scene

  • Electricity Canada and Smart Grid Innovation Network Canada Enter Collaborative Agreement

    Electricity Canada and Smart Grid Innovation Network Canada Enter Collaborative Agreement

    January 27, 2023 Electricity Canada and Smart Grid Innovation Network Canada have entered into a collaborative agreement to share knowledge and create a climate of cooperation that initiates a new direction for both organizations to better serve the professional needs of the members, industry, and community. This agreement will increase collaboration to benefit industry in… Read More…

  • Government of Canada Launches New Intake Model for Zero-Emission Vehicles Infrastructure Funding

    Government of Canada Launches New Intake Model for Zero-Emission Vehicles Infrastructure Funding

    January 27, 2023 The Government of Canada is now accepting applications from not-for-profit organizations, public institutions and governments to locally deliver federal funding from the Zero Emission Vehicle Infrastructure Program (ZEVIP). Applications will be accepted throughout 2023 and 2024. This is yet another step the government is taking to make electric vehicle (EV) charging more accessible for… Read More…

  • Southwire Casts First Copper Bar at New Plant

    Southwire Casts First Copper Bar at New Plant

    January 27, 2023 On Saturday, Jan. 21, 2023, at 12:45 p.m. (EST), the first copper bar was cast at Southwire’s new, state-of-the-art Copper Rod Plant in Carrollton, Ga. This moment is a key milestone in the start-up of the largest and most sophisticated Southwire Continuous Rod (SCR®) system in the world. “It is truly an exciting day… Read More…

  • UL Solutions Addresses Rapid IoT and Wireless Device Market Growth with Expanded EMC Testing Capabilities

    UL Solutions Addresses Rapid IoT and Wireless Device Market Growth with Expanded EMC Testing Capabilities

    January 27, 2023 UL Solutions, a global leader in applied safety science, today announced plans to expand its electromagnetic compatibility (EMC) testing laboratories in Fremont, California, Basingstoke, United Kingdom (U.K.), and Taiwan to enhance capacity for wireless device EMC testing and certification. The U.K. and Fremont laboratories are equipped with the latest testing technologies to… Read More…