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.
5K resolution
Some photographic still cameras such as DSLRs can exceed 5K resolution when capturing still images, but not when capturing video. For example, the Canon EOS 5D Mark IV announced in August 2016 has a maximum resolution of 67204480 pixels (around 30 megapixels in a 3:2 aspect ratio) which is used for high resolution still images, but it can only capture video at a maximum of 40962160 and a framerate of 30 Hz.