4K resolution
So while 4K UHD sounds like it has a pixel structures with 1/4 the area of 1080p, that does not happen with pixel shifting. Only a true 4K projector offers that level of resolution. That's why "true" 4K projectors cost so much more than 4K UHD projectors with otherwise similar feature sets. They produce smaller pixels, finer resolution, no compromising of detail or color from overlapping pixels. By comparison, the slight difference in aspect ratio between DCI and 3840×2160 pixel displays without overlap is insignificant relative to the amount of detail.
High Efficiency Video Coding implementations and products
On September 5, 2014, the Blu-ray Disc Association announced that the 4K Blu-ray Disc (as known as Ultra HD Blu-ray) specification will support 4K video at 60 fps, High Efficiency Video Coding, the Rec. 2020 color space, high dynamic range, and 10-bit color depth. 4K Blu-ray Disc will have a data rate of at least 50 Mbit/s and may include support for 66/100 GB discs. 4K Blu-ray Disc will be licensed in the spring or summer of 2015 and 4K Blu-ray Disc players have an expected release date of late 2015.