From what I saw, it depends on the RAW converter you use and the color noise removal settings.
- take the same image in RAW and sRAW at ISO12800. (I am using a 7D btw)
- develop the images in ACR 5.6 (PSE7)
- develop the images in DPP (v3.11.31)
- resize the RAW to 2592x1728 (same size as sRAW - I used bicubic resize)
- with no color noise removal in DPP the resulting images look (almost) the same
- however, with "15" as color noise removal settings in ACR the sRAW is nearly noise free while the downsized RAW still has a lot color noise in it.
- luminance noise isn't that much affected by that
Some more stuff to think about:
- sRAW: 2592x1728 = 4,27 megapixel
- RAW: 5184x3456 = 17,08 megapixel
- so RAW has exactly 4x the resolution of sRAW.
- the Canon sensors use a bayer matrix (https://en.wikipedia.org/wiki/Bayer_filter
) which has 1 blue, 1 red, 2 green sensels. That means, that the true COLOR resolution of the so-called 18mp sensor of my 7D is really 4.27 megapixel for red and blue each and 8.54mp for green.
- higher image resolution comes from interpolating, which is a polite word for "algorithmic guessing". Nothing wrong with that, one just have to know it and decide to live with the result or not.
Unfortunately I don't know the algorithms behind sRAW, but basically IF Canon did it right you get free image stacking (4 images) which should result in less noise and better color reproduction. Search the web to find noise reduction tools that use that image stacking idea - it's a working solution and if the 7D can do that on the fly for me - I'm game.
And 4.27mp native sensor resolution is plenty for the normal photo stuff
- you don't need the interpolated stuff in most cases anyway.
Good news: even the interpolated 17.08mp look very good from the 7D RAW!