Canon 5DS / 5DS R: sRAW vs Full-Res RAW Downsampled.
Get Canon 5DS DSLR at B&H Photo.
See also Canon 5DS R: mRAW is at Variance with Full-Resolution RAW in Several Ways.
Presented in my review of the Canon 5DS R, I show that sRAW is not at all like mRAW in per-pixel acuity:
The analysis includes the full-res raw image downsampled to match sRAW resolution.
Also added is a discussion of RAW, mRAW and sRAW file sizes:
RAW vs mRAW and sRAW: Camera Cropping and Downsampling and File Size
The user of the smaller formats for saving space is a marginal idea.