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

  • Celebrating 25 years: Hong Kong International Lighting Fair (Autumn Edition) Returns from October 27-30

    Celebrating 25 years: Hong Kong International Lighting Fair (Autumn Edition) Returns from October 27-30

    September 27, 2023 By Elle Bremmer Celebrating its 25th edition, the Hong Kong International Lighting Fair is set to illuminate the global lighting industry once again from October 27 to 30, 2023. This highly anticipated event, hosted at the Hong Kong Convention and Exhibition Centre, promises to showcase a wide range of state-of-the-art lighting innovations… Read More…

  • Remembering a Pillar of the Canadian Electrical Industry: Pierre Desilets

    Remembering a Pillar of the Canadian Electrical Industry: Pierre Desilets

    September 27, 2023 It is with profound sadness that we announce the passing of Pierre Desilets, a committed figure in the electrical industry, who had dedicated a lifetime to advancing safety standards, codes, and regulations. Pierre had been battling cancer with immense resilience for an extended period. His unwavering commitment to his work and his… Read More…

  • Housing Starts Flat in August

    Housing Starts Flat in August

    September 25, 2023 The trend in housing starts was flat in August at 244,507 units, up 0.8% from 242,552 units in July, according to Canada Mortgage and Housing Corporation (CMHC). The trend measure is a six-month moving average of the monthly SAAR of total housing starts for all areas in Canada. The monthly seasonally adjusted annual… Read More…

  • Lineman’s Testing Laboratories’ (LTL) Comprehensive Expertise Makes Rexel Aquisition an Ideal Partnership

    Lineman’s Testing Laboratories’ (LTL) Comprehensive Expertise Makes Rexel Aquisition an Ideal Partnership

    September 25, 2023 By Blake Marchand Earlier this year, Rexel announced the acquisition of Lineman’s Testing Laboratories (LTL), which allows Rexel to offer a complementary range of products and services and enhanced opportunities in the value-add market. LTL is a unique company with three comprehensive areas of expertise, Power Technical Services (Electrical Engineering & Substation… Read More…


Changing Scene

  • HPS Announces Ted Simpson as Vice-President of Marketing

    HPS Announces Ted Simpson as Vice-President of Marketing

    September 27, 2023 HPS is pleased to announce the appointment of Ted Simpson to the position of Vice-President of Marketing. Ted succeeds Michael Frayne as Michael transitions to the role of Senior Vice President of Power Quality and Power Conversion Solutions. Ted is a highly experienced marketing professional with over 20 years of expertise in… Read More…

  • New Funding for Apprenticeship in Alberta will Create 2,000 More Seats

    New Funding for Apprenticeship in Alberta will Create 2,000 More Seats

    September 25, 2023 A $12.4-million investment from Alberta’s government will create almost 2,000 new apprenticeship seats across the province. Alberta’s economy has momentum, and more skilled labourers are needed to support the province’s workforce, especially in the construction industry. To meet growing demand for highly skilled tradespeople across sectors, and in response to feedback from… Read More…

  • ABB Expands its Pointe-Claire Installation Products Facility

    ABB Expands its Pointe-Claire Installation Products Facility

    ABB is investing CA$16 million in its Installation Products Division manufacturing facility in Pointe-Claire, Canada. Read More…

  • Enhanced GST Rental Rebate Bill Proposed for Purpose-Built Rental Housing 

    Enhanced GST Rental Rebate Bill Proposed for Purpose-Built Rental Housing 

    September 22, 2023 On September 14, 2023, the Prime Minister announced that the government will introduce legislation to enhance the Goods and Services Tax (GST) Rental Rebate on new purpose-built rental housing, to incentivize construction of much-needed rental homes for Canadians. To build more rental housing, the removal of GST will apply to new purpose-built… Read More…