BrightSide Technologies (formerly known as Sunnybrook) created world’s first high dynamic range (HDR) display, which allows the most realistic images ever produced on a video monitor. In this article we will explain what is high dynamic range (HDR) and how this technology from Brightside works.
Dynamic range is the ratio between the maximum dark and the maximum bright a display can produce. Frequently the dynamic range of a display is labeled ”contrast ratio“ on its specs, although this is technically wrong, because true contrast ratio is measured using a standard image – a black and white checkerboard pattern, see Figure 1 –, measuring the difference in brightness between the center of white squares and the center of black squares. The contrast ratio of a display is the ratio between its maximum brightness by its minimum brightness using this test pattern.
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Figure 1: Checkerboard pattern used for measuring contrast ratio.
The problem is that the human eye has a dynamic range far higher that any display can produce. Luminance is measured using a unit called candela/m2 or cd/m2 for short. The luminance of starlight is around 0.001 cd/m2 and the luminance of a sunlit scene is around 100,000 cd/m2 – hundred millions times higher. The luminance of the sun is approximately 1,000,000,000 cd/m2. Because of such big differences in value, the luminance is usually plotted in a logarithmic scale.
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Figure 2: Dynamic range.
Conventional CRT video monitors have a dynamic range of 600:1, while good LCD video monitors have a dynamic range of 500:1. Just to give you an idea of the problem, a scene showing the interior of a room with a sunlit view outside the window have a dynamic range around 100,000:1. So this scene won’t be so realistic when shown on a conventional display.
High dynamic range, HDR, is any display capable of showing far over the numbers video monitors currently have. BrightSide technology enables displays with up to 200,000:1 dynamic range or 25,000:1 contrast ratio measured using the checkerboard pattern, and also a brightness over 3,000 cd/m2. Other interesting aspect of BrightSide’s technology is that when the screen is black, it is really black. Conventional video monitors have a residual light: when the screen is black, it is still a little bit of light there; on these monitors, black more like gray.
How can BrightSide technology achieve high dynamic range? That’s what we will explain in the next page.