Can Outdoor Digital Sign Be Too Bright

LCD screens are everywhere, even in our pockets. The phenomenal global adoption of personal display technologies such as smartphones and tablets has propelled technological innovation to new heights. The need for continuously updated communication is influencing how businesses connect with customers and make information visible to their audiences. The million-dollar question now is how to capture and hold their attention.

Hight Brightness Technology

When choosing between digital signs, end customers focus solely on display sizes. However, making the right choice regarding seemingly secondary characteristics, such as brightness and anti-reflectance, is absolutely crucial to ensure the content is presented correctly.

When engineering outdoor digital kiosks, two significant and closely interconnected issues come into play: achieving stable, sun-readable performance and effective thermal management within the enclosure. To ensure a quality image, LCD screens must feature high brightness and a good contrast ratio, defined as the ratio between the brightest white and the darkest black areas of the image. A more in-depth look about the image quality can be found in this article.

The key determinant of the contrast ratio in a real-world environment is display brightness. Brightness directly counters the effects of external light on the display. To maintain a high-quality contrast ratio, the display's contrast is directly proportional to the luminance of the backlight, especially in outdoor usage. For the best results in direct sunlight, the outdoor display should continuously operate at a minimum of 2,500 nits.

What Determines the Right Brightness?

Digital signs should provide adequate luminous intensity both day and night to ensure they are easily visible and readable by passersby. It's important to note that brighter isn't always better, as overly bright screens can pose issues.

Too bright screens:

• Are unpleasant to look at,

• Have high electricity consumption (as the LCD backlights are the main electricity consumer)

• Generate louder systems (brighter LCD backlights produce more heat, resulting in a higher fan load, which are the main noise source of the systems)

• Light pollution (Many cities have strict regulations regarding the brightness of digital signs.)

Too bright digital billboard in USA. Source: www.cbc.ca

A general rule of thumb for screen brightness is the 'two to one rule': the screen brightness should be double the normal ambient brightness. However, as we explain below, this rule can be misleading.

How to Regulate the Brightness

Outdoor digital signs are deployed in areas with changing lighting conditions. They operate 24/7, and ambient brightness varies throughout the day and night. Display brightness levels should adapt to the specific environment and ambient lighting conditions.

Some outdoor systems can automatically adjust screen brightness based on ambient lighting conditions. For example, imotion outdoor totems achieve this by regulating screen luminosity using the BH1751FVI ambient light sensor, also known as a lux meter, capable of measuring ambient light levels up to 100,000 lux.

Wavelength [ nm ], BH1751FVI and human eye comparison. Source: www.rohm.com

Its working principle is as follows: it functions as a lux meter, detecting the total ambient light nearby and then appropriately reducing the digital sign screen's backlight. The main advantage of this sensor is its response to light, which closely mimics that of the human eye.

Measurements are managed using Controlmotion technical software, which automatically regulates the display backlight. Default values for maximum/minimum ambient light and minimum/maximum backlight were determined by Infinitus R&D through testing and live applications. If necessary, these default values can be manually adjusted.

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Ambient light sensor settings in Controlmotion

Conclusion

Image quality is paramount in digital communication, especially for professional applications in public spaces that require high levels of quality and durability. In summary, adequate display brightness and proper regulation based on ambient lighting conditions are the key factors in delivering effective image presentations