Originally Posted by nathanddrews
I'm not talking about resolutions beyond 4K. I specifically called out only cameras marketed as "4K digital cameras", not 5K, etc. The point being that the 4K spec, like other resolution specs is not simply one set of values, but is a range that varies upon several factors. This is why I'm not bothered by consumer-level 4K (UHD) being at the bottom end of the range, since all other resolutions can be easily scaled or cropped down.
You just misunderstand the reasons and use of cameras with sensors with higher resolution.
A camera with 4K resolution sensor doesn't resolve full 4K resolution, and the same goes for a camera with 2K sensor, it doesn't resolve 2K.
This because when CMOS sensors RAW data is debayered it looses captured resolution.
A camera with a 2K sensor will resolve aprox. 1.5K resolution.
A camera with 4K sensor will resolve aprox. 3.5K resolution.
This is the reason that the top end cameras in its field has sensors with more pixels than the intended output format.
Example; The most used digital cinema camera, Arri Alexa has a 2880×1620 sensor, where the data is debayered and oversampled down in Camera and records/outputs 2K in the ProRes format.
In this way the full resolve of 2K in the image is contained.
Similar is done with the Sony F65 where the 20 megapixel sensor (17.6MP effective) is downsampled in camera to output full 4K resolved images.
The RED cameras records only RAW, so there the oversampling down happens in post-production.
The same principle is/should be done with scanning of film, where a film should be scanned at 6K or higher for a top quality 4K master.
70mm and IMAX is typical scanned at 8K or sometimes at 11K even though the release format is only for 4K.
The use of the full sensor resolution of these cameras/scanners, after debayering but before downsampling, is only used for VFX shot plates where the downsampling only happens after the elements are integrated in the movie, or used when they need to Up-scale the files for a higher than sensor resolution master output/release.
This means than when we in the future gets to a 8K format of 33 megapixels, the High-End 8K cameras will have sensors with 60+ megapixel sensor to be able to fully resolve 8K.
To repeat; When you see a movie in the future has been shot with a camera that has only a 4K sensor and is released as a 4K movie, it doesn't really contain Real 4K resolved details.
Cam Man has recently started a Cinematography thread where both Camera Technology, Cinematography and many other aspects of Cinema will be discussed; http://www.avsforum.com/t/1513529/cam-mans-cinematography-thread