Dithering / FRC Frame Rate Control (temporal dithering)

What dithering and FRC are

Dithering hides a lack of color depth by mixing the colors you do have. Wikipedia defines temporal dithering as "alternating each pixel's color value rapidly between two approximate colors in the panel's color space," and notes that dithering reduces banding. Frame Rate Control is the temporal version used in LCDs. It "cycles between different color shades within each new frame to simulate an intermediate shade," in the words of the FRC article, which lists a panel with native 18-bit color (6 bits per channel) showing a 24-bit image as the classic case. The modern case is an 8-bit panel acting as 10-bit, written 8-bit + FRC or 8b+2. Spatial dithering is the other family and spreads the error across neighboring pixels. Floyd-Steinberg, developed in 1975, pushes error to 4 neighbors, and the Jarvis-Judice-Ninke variant spreads it to 12. Ordered dithering instead compares each pixel to a repeating threshold pattern, so neighboring pixels do not affect each other, which suits animation. Temporal FRC adds the time axis to the same trick.

How FRC works

A native 8-bit channel has 256 levels and 16.77 million colors in total. A native 10-bit channel has 1,024 levels and 1.07 billion colors. Each 8-bit step therefore contains four 10-bit steps. TFTCentral says FRC "combines four colour frames in sequence so the eye perceives a mix," flashing "between two colour tones rapidly to give the impression of a third tone." A worked example: the 10-bit code 513 sits a quarter of the way between 8-bit levels 128 and 129, since 513 / 4 = 128.25. The panel shows level 129 on one frame in four and level 128 on the other three, and the eye averages them to 128.25. A half-step such as 128.5 alternates every other frame, which Wikipedia warns "can create a potentially noticeable 30 Hz (half frame rate) flicker" on a 60 Hz display. The quarter-step pattern repeats at 15 Hz on a 60 Hz panel and 30 Hz on a 120 Hz one.

FRC vs native 10-bit

Both reach a billion-color signal path, but the differences show up at the edges. BenQ's explainer says true 10-bit displays have 1,024 shades per RGB channel, that you will notice a difference if you compare 8-bit with 10-bit side by side, and that true 10-bit is aimed at work like retouching with pixels zoomed past 500%. For most other uses it describes 8-bit + FRC as adequate and affordable. TFTCentral warns that the quality of FRC algorithms varies, and poor ones cause a "twinkling" artifact in darker shades. It also cautions that panel bit depth is not the main cause of banding, which more often comes from inaccurate processing of color temperature, gamma, and contrast, so a 10-bit label does not guarantee smooth gradients. Where a panel does lack depth, FRC is the cheaper fix, which is why it is common.

Where FRC lives

It lives inside the spec. VESA DisplayHDR requires a 10-bit video signal per channel at all tiers, but sets the minimum driver-IC bit depth at 8-bit + 2-bit dithering (8b+2). An 8-bit panel with a good 2-bit dither therefore certifies. ITU-R BT.2100 specifies HDR coding at 10 or 12 bits per component, so the signal arrives with more depth than many panels natively reproduce. BenQ makes monitors with 8-bit + FRC panels, and it notes its own FRC displays won the TIPA Award for Best Professional Photo Monitor. TV makers rarely publish panel bit depth, and no page I fetched did for a specific 2026 set such as an LG C6, Samsung S90H, or Sony BRAVIA 9 II, so treat any per-model claim as unverified. Related definitions are in bit depth and color banding.

How to tell what your panel does

Spec sheets blur the line on purpose. TFTCentral points out that panels sold as "10-bit" are frequently 8-bit + FRC, so the label describes perceived color depth. The practical test is a smooth gradient chart on a dark ramp: native 10-bit shows fine, stable steps, while a weak FRC implementation shimmers in the darkest shades. If the panel type matters to your purchase, ask the maker for the panel's native depth rather than the marketed depth.

Why the signal path still matters

The signal into the panel has to carry the bits for FRC to use them. Active-pixel data for 3840 x 2160 at 120 Hz in 4:4:4 comes to about 23.9 Gbit/s at 8 bits per channel and 29.9 Gbit/s at 10 bits. HDMI 2.1 FRL runs at 48 Gbit/s, roughly 42.0 Gbit/s of usable data per Wikipedia's HDMI table, so a 10-bit 4K 120 Hz signal fits on a full-rate link, and a port that is only partly 2.1 may force 8-bit output or chroma subsampling instead. See HDMI 2.1 and HDMI 2.1 bandwidth tiers for how the tiers differ.

Common confusions

Dithering is not a defect: Wikipedia notes that "modest dithering can resolve" banding "without making the image appear grainy." FRC is also not frame interpolation or motion smoothing: it changes color values within a pixel across frames, not image content. The visible risk is flicker and twinkle in dark gradients, and individual sensitivity varies. If you buy a monitor for color grading, ask for true 10-bit panel depth in writing. If you watch films and play games on a TV, the DisplayHDR minimum shows that an 8b+2 panel with good processing is a legitimate design. See color gamut coverage for the other half of the color spec.