Lux Matters

Measuring the intensity of light is nothing new. However, modern electronic devices are increasingly influenced by operational requirements—autonomy, energy efficiency, etc.—that depend upon standardized, human-vision-based assessments of ambient illumination. Such assessments are measuring something called illuminance, and the SI unit for illuminance is the lux. A closely related measurement is luminous flux, the SI unit for which is the lumen.

Luminous flux corresponds conceptually to a quantity of light; illuminance, on the other hand, is the quantity of light relative to the size of the illuminated surface. Thus, it just so happens that lux is defined as lumens per square meter. For example, a 60 W incandescent light bulb might generate 850 lumens; this luminous flux does not vary according to where you locate the bulb.

But the illuminance provided by this bulb is entirely dependent on external circumstances—if the bulb’s light is distributed over a floor area of 16 square meters, you have 53 lux, which is probably adequate for walking up a staircase without tripping. That same bulb in a 1-square-meter closet gives you 850 lux, which is enough for administering first aid.

The Luminosity Function

This is where illuminance gets particularly interesting. It is essential to understand that illuminance (and therefore also luminous flux) does not reflect an objective physical quantity. Temperature is the average kinetic energy of molecules; voltage is the difference in electrical potential between two points. These measurements represent objective physical realities. Another objective measurement is irradiance, which indicates the amount of electromagnetic radiation per unit area; the SI unit for irradiance is watts per square meter.

This sounds a lot like illuminance, which is lumens (i.e., the amount of light) per square meter. The crucial difference is that illuminance is subjective, in the sense that lux values are adjusted according to the spectral sensitivity of the human eye. In other words, when calculating illuminance, 1 W/m² of red light doesn’t equal 1 W/m² of green light, because the human eye is more sensitive to green. Thus, illuminance is designed to convey information about how well a human being could see under certain lighting conditions.

Take a good look at the following curve, which is called a luminosity function.

This particular curve is referred to as “CIE photopic modified by Judd (1951) and Vos (1978).CIE stands for Commission Internationale de l’Eclairage (aka International Commission on Illumination), and as you may have guessed, this curve incorporates corrections based on the research of Judd and Vos. Much more relevant to us is the word “photopic,” which means that this particular curve is valid for human vision influenced by adequate lighting (i.e., “day vision”). A curve that conveys data for night vision would be labeled “scotopic.”

The first thing to notice here is the extreme variations within the visible spectrum (i.e., 400 to 700 nm). The values are normalized, meaning that the luminous efficiencies are expressed as relative to the maximum efficiency at 555 nm. Thus, if you had 555 nm and 450 nm light sources producing equal irradiance, a human being would interpret the 450 nm light as 20 times less intense than the 555 nm light.

The Colors of White

Usually our homes and offices are illuminated not with single-color LEDs but with bulbs that generate enough different wavelengths to give us light that appears more or less white. Nonetheless, the spectral composition of different light sources can vary significantly, and we need to take this into account when measuring illuminance.

If you are not in the habit of intuitively translating wavelength into color, this version of the luminosity function might be helpful:

Right away we can see that a light source will provide more illuminance—i.e., higher lux values—if it concentrates its electromagnetic energy near the green wavelengths. The best example of such a source is the sun; outdoor lux values are extremely high not only because the sun is so powerful but also because more of its irradiance is near the peak of the luminosity function (I suppose it is no surprise that the human eye is optimized for use with the sun). However, the luminosity curve does not mean that the ideal light source for human activity is something that generates all of its electromagnetic radiation at 555 nm. It is true that this would produce the highest ratio of irradiance to illuminance, but human beings generally prefer to live in a world with more colors than green.

What to Expect

If you design your own lux meter, you will need a way to verify that your results are reasonable. The best way to do this is with a preexisting lux meter, but preexisting lux meters cost money. Maybe you are designing your own precisely because you don’t already have one and don’t want to buy one. So here is some approximate illuminance data that you can use to assess the accuracy of your measurements.

Conclusion

We now know enough to formulate a concise definition for illuminance: the perceived level of ambient brightness, taking into account the objective light intensity and the spectral response of the human eye. Thus, the lux value in a particular environment depends on the amount of light produced by natural and/or artificial sources as well as the spectral characteristics of this light.

reference: allaboutcircuits

The latest features from calculation and rendering programs

Lighting designers use software as a design tool to complement and contribute to the design process, for everything from complex calculations to presentation renderings. In choosing lighting software, it is important to determine the designer’s required purpose: Is the software being selected to perform simple calculations, assist in space analysis, or to provide the client with a photo-realistic rendering? Once the functional intent is determined, the pros and cons of each software option can be evaluated to best suit the designer’s needs.

Lighting calculation software depends on two important components to produce accurate calculations: the selected light sources, and the surfaces within the model. All available lighting software options use one of two methods of calculation—radiosity or raytracing. To better understand how lighting software accurately calculates lighting levels, radiosity and raytracing must be differentiat

Radiosity Vs. Raytracing
Radiosity is a calculation method that divides each surface into small pieces, called patches. Each patch is calculated individually for the amount of light that enters or leaves that surface. The program then solves the system of equations in the model by determining the quantity of light on each patch as a result of the total sum of all the patches. This method works well for all matte model surfaces since radiosity is based on Lambertian reflectance calculations. Lambertian reflectance refers to surfaces that have reflected light scattered in such a way that the apparent brightness of the surface is the same regardless of the observer’s angle of view. Because of the surface dependency of the calculation, the radiosity method can calculate a model once and produce any desired view. A disadvantage to the radiosity method is that it applies to matte and diffuse surfaces only, so contributions from translucent, transparent, and specular (shiny) surfaces are not included in the calculation.

Raytracing, on the other hand, is a point-specific lighting calculation process. Calculation rays are sent outward from a particular viewpoint and the program follows each ray as it hits and reflects off different surfaces and divides into more rays. This method works for all object types including transparent, translucent, and specular surfaces. Raytracing creates beautiful renderings and presentation-quality images by visually representing light on all surfaces, including the sparkle and highlights on specular materials. Unlike radiosity, raytracing is view dependent, meaning renderings must be recalculated from each new angle. Additionally, raytracing can be a slow process, especially if the model contains a large quantity of surfaces.

All lighting software uses one or both of these two options to calculate the illuminance (the amount of luminous flux per unit area) and luminance (the intensity of light emitted from a surface per unit area in a given direction) of surfaces, and provisions to export lighting calculation data. Following is an overview of the four leading calculation software packages commonly used in lighting design offices across the United States: AGI32, Lumen Designer, DIALux, and Radiance.

source:https:radiosity

AGI32
The most recent version of the well-known lighting calculation software AGI32, version 2.0, was released by software company Lighting Analysts in February 2008. A 3-D radiosity-based point-by-point and imaging program, AGI calculates both electric light and daylight in most environments. Featuring a revised, more intuitive interface, an updated luminaire symbol library, function keys that align with AutoCAD 2004, and customizable toolkits that are movable on screen, this user-friendly AGI update has made great strides since the first release of the program in 1992. AGI was the first commercially available point-by-point program for PC platforms to perform interior computations for irregularly shaped rooms and sloped ceiling configurations. The primary goal of AGI32 is to be “as photometrically accurate as possible,” says Dave Speer, co-founder of Lighting Analysts. Although Speer points out that while renderings serve a use for client presentations, AGI’s main functionality focus is its calculations. That said, the software includes a raytracing engine that can be run on rendered views to visualize specular materials such as glass and polished stone. Lighting Analysts also produces Photometric Toolbox Professional Edition, a software program that provides creation, modification, repair, and reporting capabilities for photometric and .ies files for use in calculations. AGI32 is most useful for all lighting calculation needs including simple point-by-point surface calculations, large complex spaces with reflected light and daylight contributions, visualizing light in a space, and basic renderings.

source:agi32

DIALux
DIALux, created in 1994, is a free of charge, Windows XP–based radiosity lighting calculation software. A group of more than 90 international luminaire manufacturers funded the development of DIALux and pay to have their luminaires included with the software package. Updated and maintained by an independent company, DIAL GmbH, DIALux is frequently modified and refined to the requirements of designers. Because the software includes so many different manufacturer fixture libraries, the program retains a type of neutrality. The current release, DIALux 4.6, can be downloaded at dialux.com and is available in 26 languages. Widely used in Europe, DIALux recently began breaking into the North American market. DIALux also supports the data formats of all luminaire manufacturers globally. Features include daylighting calculations, emergency and street lighting assistants, interior scene planning and documentation, and photo-realized images with an added raytracing module for visualization of specular and transparent surfaces. Imports and exports can be done as both .dwg and .dxf files, and results can be printed or saved as a PDF. Views and renderings are saved in JPEG format with or without added raytracing. DIALux is quickly gaining notoriety as the most cost-effective software for all lighting calculations because there is no license fee. The software is applicable for complex qualitative calculations as well as photo-realistic renderings.

source: DIALUX

Radiance
The current release, Radiance 3.9, is a suite of programs for the analysis and visualization of lighting design. A highly accurate raytracing UNIX software system, Radiance was developed at Lawrence Berkeley National Laboratory in Berkeley, Calif., and is now available to run on both Windows and Macintosh OS. The major component of Radiance is the lighting simulation engine that calculates light levels and renders photography-quality images. An open source platform since 2002 (commercial use licensing fees existed previously), it is the only lighting program to exclusively use raytracing techniques and has been used by designers for the past 20 years. The advantage of Radiance over other lighting calculation tools is that there are no limitations on the geometry or the materials that may be simulated. Calculated values include spectral radiance (the relationship between luminance and color), irradiance (the relationship between illuminance and color), and glare indices. Simulation results may be displayed as color images, numerical values, and contour plots. Radiance also includes features for daylight calculations by specifying the scene geometry, materials, luminaires, time, date, and sky conditions. Radiance software is best-known for the presentation-quality, accurate renderings it produces, but renderings can be time-consuming and take up a considerable amount of computer memory. Creating photo-realistic presentation renderings is the best use of Radiance software.

source:Radiance

Selecting Software
Most lighting software includes similar features such as point-by-point calculations and daylight studies. All produce renderings, although at differing levels of quality and photo-realism. Many programs also have trial or evaluation versions along with inexpensive or free educational licenses for students.

While computers and software programs alleviate the tedious process of hand-produced point-by-point calculations, lighting designers should be wary of relying solely on computer calculations to do the work. If a designer does not understand the calculation results and how they inform the project, then the software is not an aid. Rather, a designer must be able to take the computer’s findings and know how to use the calculations and rendered images as an informative piece in the lighting design process.

source:archlighting

INTRODUCTION
The IALD International Lighting Design Awards program is the longest running award program recognizing architectural lighting design excellence. Receiving an IALD award is universally heralded as the top honor in the lighting design industry. Begun in 1983, the IALD International Lighting Design Awards honors lighting design that reaches new heights, moves beyond the ordinary, and represents excellence in aesthetic and technical design achievement.in this article we introduce IALD program and provide you with information about the process of submitting a project to the IALD International Lighting Design Awards.

ELIGIBILITY

Anyone may enter a project for an award. The project must be a permanent architectural lighting design solution. A specific project completion date is listed on each year’s Call for Entries document. Projects entered the previous year can be resubmitted, provided the project still meets the criteria and did not previously win an award from the IALD.

PROJECT CATEGORIES

The IALD International Lighting Design Awards does not use project categories for submission, judging, or awards for any of the projects. All projects are judged together and in a random order.

NOTE: Any installation must be intended to be in place for at least two years. Lighting design for temporary installations – such as special events, theatrical performances, light sculpture, light art – are not eligible for consideration.

AWARD CATEGORIES

The IALD encourages submissions of all types and sizes. There is no minimum or maximum number of awards granted. Awards of Excellence and Merit will be based on points earned for both aesthetic and technical design achievement.

Recognition in the form of a Special Citation may be given for a particularly innovative aspect of a project’s lighting design, if that project does not earn enough points to receive an Award of Merit or Excellence.

The top honor of the IALD International Lighting Design Awards, IALD’s Radiance Award for Lighting Design Excellence, will be presented to the project that is judged among all submissions to be the finest example of lighting design excellence (based on the highest point score)

NOTE: There is no requirement that an award be made in every category. If no project reaches the required point score in a given category, no award will be granted in that category.

SUSTAINABILITY

In recognition of the importance of sustainable design to the profession of lighting design and to the world in which we live, the IALD in 2004 instituted an awards category for sustainable design.

In 2018, the IALD awards program eliminated the specific additional award of sustainability with the expectation that all award-winning projects would apply sustainability in design.

SUBMISSION REQUIREMENTS

Images must not include any text or materials added in post-production. All references to the submitting firm must be removed from images. Failure to comply will result in image disqualification.

For the purposes of this competition, an “image” is defined as one photograph. Up to three images per slide is permitted, and 10 images total per project is allowed. A minimum of six images is required for every submission. Image files containing multiple photographs, drawings, or renderings combined into one digital file will have each separate image counted toward the project maximum of ten images.

Projects containing kinetic lighting may usbmit a video file to help explain these kinetic lighting elements. No walkthroughs of non-kinetic projects will be allowed.

TIPS FOR VISUALS

The quality of the images and video clips are important in the judging process. Although the images do not need to be professionally photographed, they should be of the highest quality to illustrate the designer’s work. Color photography is required.

You have to avoid the use of fill light when photographing the sites. If you must use fill light, clearly identify which images include fill light. Undisclosed fill light and digital alternations/manipulations may be grounds for disqualification as it may alter the judge’s perception. Please also identify any areas in the images that were not the work of the submitting designer.

Entrants are encouraged to include images that show the project in use, in context with its surroundings, and from a human vantage point. Smaller scale projects should show more detail rather than reducing the number of images. If the project includes exterior lighting, at least one daytime photograph is recommended. If plans or drawings are required to describe the lighting solution, include images of the essential information.

NOTE: Daylit images make judging the success of artificial lighting nearly impossible. If a submission includes more than one or two images that include daylight, the entrant should indicate why this is so [daylight being a focus of design technique, main use of environment is during daylight hours, etc.].

JUDGING PROCESS

The judging for the Awards program is rigorous, to uphold the integrity of the process, and blind, meaning that no judge knows the identify of the firm or individual involved in the development of the submitted projects. Judges gather at the IALD Headquarters office in Chicago, IL USA for three straight days of judging, and only those projects demonstrating consistent design quality and technical expertise receive award recognition.

Scoring is quantitative, with each judge confidentially assigning a numeric value to each criterion after a period of discussion. Ballots are tallied and results kept confidential until judging concludes. There is no point during the process in which judges are made aware of where a specific project stands in terms of receiving an award.

reference:IALD

AWARDS OF MERIT

APPLE MICHIGAN AVENUE, CHICAGO