GoKawiilis a senior reviewer covering TVs and audio. He has over 20 years experience in AV, and has previously been on staff at Digital Trends and Reviewed.
At the Los Angeles Convention Center, two 85-inch TVs sat side by side inside the Nanosys meeting room at Display Week — a yearly business-to-business convention focusing on the technology that goes into displays of all types. One TV was a mini-LED panel with super quantum dots, and the other was an RGB LED — this year’s hottest TV trend. Both TVs were showing the same content at the same time to highlight the differences between the two technologies — or more specifically, to show the potential failings of RGB LED backlights when compared to super quantum dot (SQD), which uses blue LEDs for the backlight.
I should probably mention that Nanosys made the quantum dots in the first TV.
During the side-by-side demo, the TVs played the same content simultaneously for easy comparison. Photo by John Higgins / The Verge
The TV on the right, with the Nanosys super quantum dots, was labeled as the TCL X11L — the striped lower grille confirming as much — and the other was most likely the TCL RM9L. Nanosys wouldn’t confirm as much, but I’ve seen the RGB LED TVs from Hisense, Samsung, LG, and Sony in person, and it wasn’t any of those. Jeff Yurek, vice president of marketing at Nanosys, informed me that both TVs were in Filmmaker Mode and color was set to native to allow both to hit the largest gamut possible.
As a quick refresher, RGB LED TVs use red, green, and blue LEDs grouped into zones to create a colored backlight based on the image displayed on screen. Theoretically, this gives the TV more vibrant and saturated colors than mini-LED TVs like the X11L with blue backlights, without needing to rely solely on the quantum dots. The primary potential issue is that the colored light provided by the backlight will bleed into adjacent pixels or zones that differ in color, resulting in what’s called color crosstalk. Practically, this could cause the red of a bright shirt or hat to cause the skin of the wearer to have a reddish hue. And that’s exactly what this demo showed.
One of the demonstrations alternated between this slide with two rows of boxes and a row of crosses and the next slide. Image: Nanosys On the RGB LED TV, when the white cross was introduced to the top row of boxes, there was a shift in the color intensity of those boxes. Image: Nanosys When squares without a white cross were measured, the RGB LED TV’s color points were slightly wider than for SQD. Image: Nanosys The white cross caused the green color point (top of the triangle) and blue color point (bottom left of the triangle) to move between the SQD color points. Image: Nanosys
During the entire demonstration, the same video feed went to both TVs. One slide showed three rows: two rows of boxes with the primary and secondary colors — blue, green, red, cyan, magenta, and yellow — and the third with a thin white cross on a black background under each colored box. The top row of boxes would then alternate between a solid box and one with a white cross inside it. On the RGB LED TV, as the white cross appeared in the top row, it was easy to see the color of the area around the cross get a bit lighter and less saturated. The color crosstalk didn’t just happen within the top row of boxes; the box color from the middle row also visibly bled into the bottom row of crosses. This shows in the TVs’ BT.2020 color gamut measurements as well, with the introduction of the white cross diminishing overall BT.2020 coverage, most dramatically with the blue and green color points.
But unless you’re a measurement nerd like me, you don’t watch solid blocks of color on your TV for fun. The effect is also present with skin tones — something that, as humans, is easily noticed. Just as the color of the blocks bleeds into the white cross, so does a colored background into skin tone; still images of a woman’s face with a colored background caused her skin tone to shift toward the background color. To make sure my eye wasn’t causing the color bleed, as opposed to the TV, I used a scope to focus just a portion of the woman’s face, blocking out the rest from my view. I could still tell which background color was displayed by the change in hue of her skin.
While BT.2020 measurements stayed at a consistent percentage on the SQD TV, the percentage went down on the RGB LED TV as the color patch got smaller. Image: Nanosys
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