Display Resolution

显示分辨率 The spatial sampling dimensions of a digital image are typically expressed as the number of horizontal pixels multiplied by the number of vertical pixels, such as 1920×1080 or 3840×2160. For fixed-pixel panels, this also represents the physical pixel matrix; for video files, more accurately, it represents the luminance sampling grid of the encoded frame.

Resolution is not the same as visible sharpness. Lens, focus, sensor sampling, demosaicing, noise reduction, master, compression, scaling, viewing distance, and screen size all affect detail. A 4K file may originate from a 2K master or be upscaled, and a 1080p file may retain more usable detail than a heavily compressed 4K file. Pixels are not always square. Standard-definition video, such as on DVDs, is commonly stored at 720×480 or 720×576, but relies on pixel aspect ratios and display aspect ratios to be rendered as 4:3 or 16:9. Calculating aspect ratios based solely on stored pixels will result in incorrect shapes. Cropping, non-square pixels, and the effective image area can also cause the same nominal format to appear differently on screen.

“1080p” combines vertical pixel count with progressive scan in its name, while “1080i” denotes interlaced scan; simply stating 1920×1080 does not fully specify the scan method or frame rate. Additionally, 4K and 8K have different definitions for width between television and digital cinema.

Chroma subsampling causes chrominance signals to use a lower spatial resolution than luminance; for example, the chroma grid in 4:2:0 video is subsampled both horizontally and vertically. The primary resolution reported by media tools typically refers to the luminance frame and does not indicate that each color component has the same number of samples.