What are SD, HD, Full HD, Ultra HD

Preface

Normally, the resolution of our common computers is 1280×720 or 1920×1080. What category do they belong to? What level does this value belong to? Let us study it systematically.

Screen resolution refers to the number of pixels displayed horizontally and vertically on the screen, and the unit is px. It determines the settings for how much information is displayed on the computer screen, measured in horizontal and vertical pixels. For example, the resolution of 1280×720 means: the number of pixels in the horizontal direction is 1280, and the number of pixels in the vertical direction is 720. What we need to be clear is that pixels are indivisible and define the smallest unit of a digital sequence to represent an image.

SD:

SD is the abbreviation of Standard Definition, which refers to a format with a vertical resolution below 720p. Video formats such as VCD, DVD, and TV programs with a general resolution of about 400 lines are Standard Definition.

Typical standard definition resolution: 480×320, 640×480.

Note:
"P" is progressive, which means progressive scan.
"I" interlace is interlace scanning.

HD:

HD is the abbreviation of High Definition, which refers to a display with a vertical resolution greater than or equal to 720p, and the size is generally 1024×720p and 1920×1080i.

HD has three display formats:
720P (1280×720, non-interlaced, field frequency is 24, 30 or 60);
1080i (1920×1080, interlaced, field frequency 60);
1080p (1920×1080, non-interlaced, field frequency is 24 or 30)

Full HD:

Full HD is the abbreviation of Full High Definition. It means that the physical resolution of the screen meets 1920×1080, and it can handle the screen resolution of 1080p format. The full HD screen will not change due to changes in the signal.

Typical Full HD resolution: 1920×1080p.

Ultra HD:

Ultra HD is the abbreviation of Ultra High-Definition. It is the next generation technology of HD, Full HD, Quad HD (eight times HD). The "Ultra High Definition UHD" standard recommended by the International Telecommunication Union (ITU) calls a display with a physical resolution of 3840×2160 (4K×2K) and above as ultra high-definition, which is FHD (1920X1080) wide and high Two times each, four times the area.

Ultra HD defines two resolutions:
The pixels of 4K UHDTV are 3840×2160p. The total number of pixels is 4 times that of Full HD.
The pixels of 8K UHDTV are 7680×4320p. The total number of pixels is 16 times that of Full HD.

Conclusion:

In the case of the same screen size, the higher the resolution, the finer and more delicate the display effect. As far as the screen of the same size is concerned, when the screen resolution is low (for example, 1280×720), there are fewer pixels displayed on the screen, and the size of a single pixel is relatively large. When the screen resolution is high (for example, 1920×1080), there are many pixels displayed on the screen, and the size of a single pixel is relatively small.