Interlaced High Definition (HD) television stores a 1920×1080 grid of square pixels in a 16:9 frame. The number 1080 counts active vertical lines.
The letter i marks a frame split into two fields. That scan is 1080i. It was the usual High Definition Television (HDTV) broadcast format alongside 720 Progressive (720p). 1080 Progressive (1080p) draws all 1080 lines every frame on the same grid and is also called Full High Definition (FHD). 1080i keeps the grid and changes only the scan.
How the Two Fields Are Drawn
The frame is not painted in one pass from top to bottom. Half the active lines go out, then the other half, and the display has to interleave them.
- Odd lines, then even lines. One field holds the odd-numbered active lines. The next field holds the even-numbered lines. A display weaves those fields back into a single frame. Lines in the blanking interval are outside the count of 1080.
- Same stored grid as 1080p. Both use 1920×1080 square pixels at 16:9. 1080p draws the full set of lines on every frame. 1080i sends one field, then the other.
- Fewer lines in standard definition. Older interlaced television is Standard Definition (SD): 480 Interlaced (480i) in National Television System Committee (NTSC) regions, and 576 Interlaced (576i) in Phase Alternating Line (PAL) regions.
- A count of pixels, not a density. The 1920×1080 grid says how many pixels are stored. It does not say how large they are on a screen. That density is Pixels Per Inch (PPI).
Field Rates and Motion
Each field is its own moment in time. The rate decides how many of those moments fit in a second, and a bad weave shows the gap.
- Two common field rates. Speed is measured in Frames Per Second (FPS). Fifty fields make 25 frames, and 60 fields make 30 frames. PAL regions use the integer 50-field rate. The usual NTSC broadcast rate is 59.94 fields, which is 29.97 frames. Timing kept by the Society of Motion Picture and Television Engineers (SMPTE) preserves that slightly slow clock so the signal stays compatible with older color television.
- Combing on motion. Interlace can show combing on motion if a display fails to deinterlace. The odd lines and the even lines were captured a field apart, so a moving edge becomes a row of teeth when both fields are drawn as one still frame.
- A normal mode on a digital link. This scan is a standard picture format on High-Definition Multimedia Interface (HDMI).
- Dynamic range is a separate choice. Broadcast 1080i is usually Standard Dynamic Range (SDR). High Dynamic Range (HDR) is more often paired with progressive Ultra High Definition (UHD). After the fields are woven, a panel can light the picture as Red Green Blue (RGB).
Picture Format Family
These formats are named from the active vertical line count and a final letter for the scan. The two 1080-line rows store the same square-pixel grid.
| Format | Active Grid | Scan |
| 480i | 720×480, non-square | Interlaced standard definition |
| 480 Progressive (480p) | 720×480, non-square | Progressive standard definition |
| 576i | 720×576, non-square | Interlaced standard definition |
| 576 Progressive (576p) | 720×576, non-square | Progressive standard definition |
| 720p | 1280×720 | Progressive high definition |
| 1080i | 1920×1080 | Interlaced, two fields per frame |
| 1080p | 1920×1080 | Progressive, every line each frame |
| 1440 Progressive (1440p), Quad High Definition (QHD) | 2560×1440 | Progressive, square pixels |
| 2160 Progressive (2160p) | 3840×2160 | Progressive ultra high definition, often labeled 4K |
| 4320 Progressive (4320p) | 7680×4320 | Progressive, often labeled 8K |