OFFICE LIGHTING
Is 500 lx really enough?

The number 500 lx often appears as the main goal when planning office lighting. When a measurement on a work desk shows this value, it is easy to conclude that the task is solved. However, the same amount of light does not necessarily mean the same quality of light.

Two offices can have an average of 500 lx on the work surface, yet provide a completely different experience. In one, you can work comfortably for hours, while in the other, reflections on screens, too strong contrasts, or poor lamp placement will quickly cause discomfort. Therefore, 500 lx should be seen as an important design data, but not as a final confirmation that the lighting is good.

What does 500 lx actually mean in the office?

Lux, or lux, is a unit of measurement for illuminance. It indicates how much light falls on a given surface. When we talk about 500 lx in an office, we usually mean the maintained average illuminance of an area where visual tasks are performed, such as reading, writing, or working on a computer.

The HRN EN 12464-1:2021 standard defines the requirements for lighting in indoor workplaces about visual comfort and efficiency. For many common office tasks, 500 lx serves as a reference value, but the standard does not only consider the amount of light. It also takes into account its uniformity, glare limitation, color rendering, and the immediate environment of the work task.

Where the value is measured is also important. Five hundred lux on an empty table does not automatically tell you how much light a person receives in their field of vision, what the space around the screen looks like, or whether there will be unpleasant reflections on a shiny surface.

Is more light always better?

Not necessarily. In a study of preferred office lighting, subjects were exposed to levels of 75, 300, 500, 750, and 1200 lx. They achieved the best cognitive task results at 500 and 750 lx, while 500 lx was subjectively rated as the most comfortable during the rest phase. Increasing to 1200 lx did not improve the results further.

This does not mean that a formula has been found that works for every office. The study was conducted in a controlled room with 28 younger subjects, with artificial lighting and without the real conditions of an open office. The authors themselves state that the needs of the users are influenced by the type of task, age, daylight, uniformity, and glare.

A useful conclusion, therefore, is not that every office should have exactly 500 or 750 lx. It is more important to recognize that increasing illuminance beyond a certain level may yield diminishing benefits, while unresolved light quality problems remain.

Quality office lighting doesn’t fit into one number.

When comparing lighting solutions, it is necessary to observe several properties simultaneously.

The table shows why a project should not be judged on just one item of technical documentation. Even two lamps with the same number of lumens, the same color temperature, and similar CRI may not give the same result in a room.

Glare is not solved by blindly reducing the light

Discomfort is often not caused by too much light in the office, but by a very bright source being in the wrong part of the field of vision. Reflections from screens, glass partitions, or shiny desks can also be a problem.

Therefore, glare is solved by a combination of the correct position and optics of the lamp, its illuminating surface, viewing angle, and the arrangement of the workstations. Simply dimming the entire space can eliminate some of the discomfort, but at the same time leave too little light for work.

Evenness is not the same as a completely uniform space

The work surface should not have abrupt transitions between very light and dark areas, as the eye has to constantly adjust. However, the office does not have to look like a uniformly lit box.

Good office lighting can combine:

• uniform functional light at workplaces
• pleasant vertical illumination of faces and walls
• softer light in relaxation and informal meeting areas
• accent or decorative light that gives a space its identity
• lighting control according to available daylight and how the space is used.

Such a layered approach allows the office to meet technical requirements, but also not appear cold and impersonal.

Why color temperature isn’t the whole story about alertness

It is often stated in a simplistic way that cooler light always increases concentration, and warmer light always relaxes. The actual answer depends on the time of day, previous exposure to light, duration of exposure, intensity, and spectral composition of the source.

Reviews of research on daytime light exposure show that the results are not entirely clear-cut, especially when subjective feelings of wakefulness are compared with objective physiological indicators. Color temperature can therefore be a useful description of the appearance of light, but it is not sufficient to predict its biological effect. Two sources labeled 4000 K may have different spectra, just as two light bulbs labeled 3000 K may not render materials and colors the same way.

Instead of automatically selecting the coldest possible light, it is necessary to look at the whole: the type of work, the time of use, the presence of daylight, the interior finishes, and the needs of the people who live there.

Checklist before accepting an office lighting project

Before we conclude that the lighting is solved because the calculation shows 500 lx, it is worth checking the following:

1. Is the required illumination achieved on the actual work surface and for the specific task?
2. Are there big differences in brightness between the table, screen, and background?
3. Do users see very bright sources directly from their usual positions?
4. Do reflections appear on monitors, glass, or shiny furniture?
5. Do leather, wood, textiles, and other important surfaces look natural?
6. Can the lighting be adjusted to daylight, different tasks, and users?
7. Are work, communication, and rest areas lit according to their purpose?
8. How will the result change after source aging, contamination, and future equipment replacement?

The answers to these questions often reveal more than just the maximum or average value measured by a lux meter.

The goal is not more light, but better light.

Five hundred lux is not a magic threshold beyond which any office becomes comfortable and productive. It is an important reference value that should be related to the type of task, the users, and all other characteristics of the lighting environment.

Quality office lighting is created when technical and decorative light work together: workstations have the necessary visibility, glare is controlled, colors and materials look convincing, and the space retains character. It is in this transition from filling a number to shaping a complete experience that serious lighting design begins.