Subpixel Dimming Pixel-level (per-pixel and per-subpixel) dimming on self-emissive OLED

What the term means and what it does not

"Subpixel dimming" is a phrase searchers use, and I found no source that defines it as a product feature or a standard. LG, Samsung, Sony and VESA do not use it in the pages I loaded. The established terms are Pixel Dimming and Pixel Level Dimming, the marketing names for per-pixel light control on OLED. A French display glossary notes that Hisense and LG both use the name Pixel Dimming to present one of the advantages of OLED, namely that each pixel can be lit or switched off independently, and an English explainer says LG first used Pixel Dimming and then Pixel Level Dimming on some OLED models. Neither describes a different technology: the names point at self-emissive pixels, and the "sub" in the search term reflects that the control reaches the subpixels.

How OLED does per-pixel and per-subpixel dimming

An OLED pixel emits its own light, so there is no backlight to dim. TFTCentral writes that OLED pixels emit light at a sub-pixel level, and that to display black you can simply turn off the sub-pixels so they emit nothing. LG's OLED page makes the same claim in consumer terms: self-lit pixels that turn on and off independently, giving perfect black and infinite contrast without a backlight. Inside each pixel the subpixels are separate emitters or separate filtered channels. On LG's WOLED panels, TFTCentral explains, each subpixel emits white light (usually a blue and yellow combination) through a red, green or blue color filter, with an extra white subpixel added to recover the brightness the filters block. That makes four subpixels per pixel, so a 4K WOLED panel has 33,177,600 subpixels (8,294,400 × 4). See WOLED and QD-OLED for the two layouts.

OLED vs LCD local dimming

An LCD has one backlight shared by many pixels, so it dims in zones. Tom's Guide notes that only a few years ago it was common to see about 100 dimming zones, while today several thousand zones is common in mid-range TVs, and mini-LED backlights are LEDs measuring about 0.004 to 0.008 inches. Even 5,000 zones on a 4K panel means each zone covers about 1,659 pixels (8,294,400 ÷ 5,000). When a bright object sits on a dark scene, the zone around it lights up, and Tom's Guide says light can still find its way around dimming zones, producing blooming, which has become less of an issue as zones shrink. TFTCentral's count for an Ultra HD OLED, 8.3 million dimming zones, is the extreme end of the same scale: one zone per pixel. See full-array local dimming and blooming.

What the black level difference looks like in specs

VESA's DisplayHDR CTS 1.2 shows the gap in numbers. In its dual-corner-box black level test, which keeps white in two corners while measuring the screen center, an LCD tier must reach 0.05 cd/m² for DisplayHDR 1000 and 0.02 cd/m² for DisplayHDR 1400, while the DisplayHDR True Black tier requires 0.0005 cd/m². That is 40 times darker than the top LCD tier. VESA also requires static contrast ratios for 2D local-dimming backlights of 30,000:1 for the 1000 tier and 50,000:1 for the 1400 tier, whereas an OLED's off pixels are limited by the room, not by zone size.

The specification also fixes the white in the corners at 1,050 cd/m² for the 1400-class tiers. Dividing by the black limits gives a derived contrast of 52,500:1 for the LCD tier (1,050 ÷ 0.02) and 2,100,000:1 for True Black (1,050 ÷ 0.0005). Pixels per dimming zone on a 4K screen make the same point from the other side: 100 zones means 82,944 pixels share one brightness, 1,000 zones means 8,294, 5,000 zones means 1,659, and 8.3 million zones means 1.

What the room does to the advantage

Per-pixel black is perfect in the dark and not in daylight. TFTCentral measured how perceived black depth changes as room light rises from 0 to 500 lux across OLED monitor panels. At 0 lux every OLED reaches the same true black, because the pixels are off. As ambient light rises, the panel technology and coating decide the result: matte WOLED panels were about twice as good as second-generation QD-OLED at perceived black depth and about 2.7 times better than first-generation QD-OLED, and second-generation QD-OLED improved on the first by about 36%. Those figures come from monitors, not TVs, and the lab says the difference becomes more noticeable as the room becomes brighter.

The trade-offs of per-pixel control

Switching pixels off does not remove OLED's own limits. Brightness is limited when large areas light up: Tom's Guide measured the LG C6 at 1,355 nits on a 10% window and 236 nits on a 100% window, a drop of 5.7 times that the HDR brightness window entry explains. The white subpixel that helps brightness is also the root of WOLED's color trade-off, covered in the WOLED saturated color deficit entry.

Where it applies

It applies to OLED TVs generally: LG's WOLED sets such as the C6, whose lab figures are above, and the QD-OLED sets built on Samsung Display panels. It does not apply to LCD sets with local dimming, including mini-LED models: those dim by zone, however fine the zones are. The mini-LED vs OLED comparison and QD-OLED vs WOLED guide cover the choice.