Digital Signage: Darker Darks are the Key to LED Contrast Ratios

In attempting to digitally recreate real life on a screen, one of the most important metrics to consider is contrast ratio.
Digital Signage: Darker Darks are the Key to LED Contrast Ratios
Like

A version of this article appears on Nanolumens

In attempting to digitally recreate real life on a screen, one of the most important metrics to consider is contrast ratio, which the National American Standards Institute defines as “the absolute difference in luminance between the peak white and black levels” of a display. While the resolution, pixel pitch, and color space receive more attention from digital display customers and manufacturers alike, the overall picture quality might actually be more dependent on contrast ratio. The reason contrast ratio is such a crucial determinant in image quality is that distinct elements of an image only stand out relative to their surroundings. If a display is unable to accurately differentiate the brightness of those surroundings from the brightness of the distinct image element in question, the resulting on-screen picture will fail to resemble true life.

To help put this in context, think about the last time you looked at the sun during the middle of a bright day. Hopefully, you didn’t stare too long but what you likely saw was that despite the brightness of the surrounding sky, the sun stood out. Why? Because it was so much brighter. To accurately show this same scene digitally, a display will have to be capable of extreme brights but outside of LED, most technologies fall short, especially when the display environment features high levels of ambient light.

Now think about the last time you saw a full moon on a clear night. The moon likely stood out quite brilliantly. Why did it stand out so well? Not because the moon was particularly bright but rather because the night sky around it was so dark. For a display to recreate what you see with your own eyes, it will need to recreate that same darkness. This is nearly impossible for LCD displays and projection technology to accomplish because these technologies require light to represent their images. LCD displays use LED backlight filtered through liquid crystals to display their content, but these backlights are not individually adjustable. Their brightness can be turned up and down in general regions to create a “dynamic contrast ratio,” but the LED pixels themselves are not locally controllable. Similarly, projectors create their images by casting filtered light onto a surface, but they cannot project darkness.

Where LED differs from these two technologies is that not only are LED displays far brighter than either LCDs or projectors but the brightness of pixels within an LED display can be individually adjusted and even turned off entirely to create a true black. So, if you need a region of pixels to mimic the brightness of the sun as the surrounding pixels match a bright blue sky? LED can do that better than any other technology. Or do you need pixels to go completely black around a distinct image that’s just barely brighter than black? Again, LED can do this where others cannot.

Contrast ratio, alongside peak white and black levels, are important specifications to keep in mind when making any digital display decisions.

A version of this article originally appeared on Nanolumens

Ready to learn more about digital signage? Subscribe to our D=SIGN newsletter!

Please sign in

If you are a registered user on AVIXA Xchange, please sign in