HD or UHD Explained
TECH TIPS - RESOLUTIONS, UHD & HD EXPLAINED
FIRST, WHAT IS A PIXEL?
A pixel is a tiny point of illuminated colour and the smallest controllable element in a display. Thousands (or even millions of these pixels) are combined across the display to create an image, similar to how jigsaw pieces reveal a larger image when combined.
WHAT ARE IMAGE RESOLUTIONS?
Image resolutions refer to the number of pixels in an image, the higher the resolution the higher the image quality. Image resolutions are usually referred to by the number of pixels wide and the number of pixels high. For example, 1920x1080 would be an image which is 1920 pixels wide by 1080 high.
WHAT IS HD?
HD, or high definition is a designation given to resolutions that are considerably above 576 vertical pixels (In Europe). The most common HD resolutions are:
1280x720 also known as HD Ready or 720p
1920x1080 also known as Full HD or 1080p
2560x1440 also known as Quad HD or 1440p
WHAT IS 4K UHD OR ULTRA HIGH DEFINITION?
4K, UHD or Ultra High Definition are all common names for resolutions which are at least 3840x2160 pixels. The most common UHD resolutions are:
Also known as 4k, UHD or 2160p
WHAT IS 4K 4096X2160?
This resolution mainly used in Digital Cinema production.
WHAT IS 4K HDR?
Here is a link to our in-depth HDR FAQ
WHAT DO 10.2G AND 18G MEAN?
When we talk about 10.2G and 18G we are referring to the bandwidth capabilities of devices such as extenders, switches, and splitters etc. Bandwidth is measured in gigabits therefore 10.2G and 18G would be 10 gigabits, and 18 gigabits.
10.2G is the maximum bandwidth the device can operate at. This means the amount of data, including the image and audio among other things that can be sent. The higher the bandwidth, the more data it is possible to send to a display, resulting in higher resolutions, better quality audio and other improvements including higher refresh rates and a wide range of colour spaces.
WHAT ARE REFRESH RATES?
Refresh rates are the amount of times a display redraws a scene per second. This is measured in frequency (Hz) for example, 60Hz would mean the display is redrawing the scene 60 times per second. Higher refresh rates make movement on screen appear smoother. This can be hard to visualise so here is a gif to help illustrate the difference:
WHAT IS COLOUR SPACING AND WHAT DO NUMBERS LIKE 4:2:0 AND 4:4:4 MEAN?
Digital signals are often compressed to use less bandwidth. One way in which they are compressed is by using colour spacing or chroma subsampling. Chroma subsampling is often written as 4:2:0, 4:4:4 or similar numbers. 4:4:4 represents the full signal without any compression and full colour information, 4:2:2 has half the chroma of 4:4:4 and 4:2:0 a quarter of the colour information is available. Simply put, the human eye struggles to notice very slight variances in colour and therefore colour sampling (chroma subsampling) is used to compress data to a smaller size for transmission.
WHY DO I NEED 18G?
Simply put, for incredibly high quality 4K images without compression. If you want to use 4K at a 60Hz refresh rate with no compression, then you need 18G capable technology. Or if you’re using something which features HDR (link) such as a 4K satellite or cable TV receiver, you need 18G to send the large amount of bandwidth required.