The Wave's sensor has two readout modes, 4K (4096px per row) and 2K (2048px per row), which correspond to the Width setting in the on-camera menu. 2K uses subsampling (row and column skipping):
While this sensor does have a binned 2K readout mode, it's slower than reading out the full 4K, so it isn't useful in practice. The fast subsampled readout allows much higher frame rates in 2K, but with reduced image quality:
Subsampling does not increase the ISO of the sensor (as binning would), so proportionally more light is needed to achieve good exposure at the higher frame rates enabled in 2K mode.
Subsampling introduces more aliasing due to the sparse distribution of sampled pixels. See below for an example of this effect and an alternative way of capturing 2K at intermediate frame rates.
The 2K readout mechanism, combined with higher frame rates, introduces more noise as more electrical switching is happening at the sensor with less settling time.
The HDMI preview quality is limited by hardware constraints to half resolution, so the 2K preview can be difficult to use for focus.
For these reasons, the 2K readout mode is best used for scientific applications where image quality is less important than maximum frame rate. The 4K readout mode is best used for cinema applications where image quality is highest priority.
It's also possible to shoot cropped 2K while in 4K readout mode by setting the Height to 1088px and manually cropping out the center of the image. In this configuration the maximum frame rate is 833fps. The image quality will be better than subsampled 2K, but obviously not as good as full 4K. See below for an example of 4K, cropped 2K, and subsampled 2K.
