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.
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.
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.
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BrightSide technology uses LCD technology. Usually LCD displays have a backlight provided by CCFL (Cold Cathode Fluorescent Light) tubes. That’s why even when the LCD screen is black it is not actually black, it still has some residual light: the tube is still turned on. The main idea of BrightSide technology is to remove this CCFL backlight and use several LEDs instead, a technology they call IMLED (Individually Modulated Array of LED backlights).
The brightness of each LED is controlled by an 8-bit signal, so each LED has 256 brightness steps (zero would mean “tuned off” while 255 would mean “totally turned on”; a “128” value would turn on the LED with 50% of its luminance, a “64” would turn on the LED with 25% of its luminance and so on). The first display launched with this technology – called DR37-P (which is a 37” panel) – has 1,380 white LEDs behind the LCD screen.
So, the idea is quite simple. Instead of having just one light source behind the LCD screen that is turned on all the time with the same brightness, BrightSide technology displays use several white LEDs where each one can have its brightness controlled (256 different brightness steps).
In Figure 5, you can see BrigthSide technology in action. On the left side you can see the original image sent to the display. On the right side you can see how the LEDs are illuminating the LCD screen. As you can see, each LED can be turned on using a completely different brightness. On the center, you see the final result, how the image is displayed on a monitor using this technology.
So far, just one LCD panel using this technology was released, DR37-P – which manufacturing is outsourced. We had the chance of seeing one and the image quality is really impressive, far better any LCD or plasma display available on the market. Right now BrightSide is focusing on the high-end professional market, like movie studios. To reach the regular consumer market, BrightSide is looking for partners and licensees for their technology – i.e., other companies that can manufacture displays using their technology.
We are talking about a very expensive display, and its price will drop only with mass production, which will happen only if they find partners and/or licensees, since we are talking about a small Canadian company with a great idea. Otherwise it will be one more obscure company selling to a niche market – if much: if companies in that niche market don’t buy their product, they are gone.
- For more information: https://www.brightsidetech.com