The resolution of this standard is 4,096 x 2,160 pixels and therefore corresponds to an image ratio of 17:9. However, as monitors usually have a 16:9 aspect ratio, thin black bars appear at the top and bottom when displaying real 4K content on monitors and the like, which adjust the image to the correct format. The term 4K originally comes from the professional film and video production industry. This is why it is actually referred to as DCI 4K (DCI = Digital Cinema Initiatives), which is sometimes also referred to as Cinema 4K.
