they are not either at the top or bottom, sensor are linear capture, not like film, the range is larger vs smaller, that is the difference and if you care more about highlights then you expose less and save more, if you care more about shadows you expose longer and lose more highlights
If your talking strictly about discrete levels, yes, but technically speaking you could make the same argument about film. Were talking about dynamic range, though...successive stops of increased tonal range. Every additional bit IS a doubling of the total DR, so in that sense, no, its not linear.
and don't forget that DxO "print" numbers are based on a normalization to 8MP so you can things like 14.5 stops on a 14bit camera
I'd like to know exactly how the simple act of downscaling magically fabricates additional DR you did not start out with. In the case of the D800, at least according to DXO, you magically gain a full 2/3rds of a stop extra DR
simply by scaling all of your images down to an 8x12" print. Well, either you can gain what you don't have with a little bit of resizing-foo...and that would apply to ALL cameras, including Canons; or no amount of digital magic can fabricate DR, and Mount Spokane is absolutely correct that DXO is weighting their results in favor of Nikon. Seeing as the gains Nikon has made with the D800 surpass what seems plausible and reasonable, my commitment to DXO's print DR (which I previously trusted) is wavering.
Personally, I'm of the camp that if you start out with 13.8 stops of native DR strait off the sensor, you have 13.8 stops of DR. If you muck around with a digital image in post to fabricate additional data
, that is not true dynamic range, and technically speaking you should be able to do the same thing with images from ANY camera to magically increase DR. In this case, DXO claims about 1.6 times as many additional levels of luminance than you got strait out of the camera...around an additional 10000 levels!! For the math, 1 extra stop of DR is 2^15, or 32768 levels, where as 14 stops of DR is 2^14, or 16384 levels, so a gain of 2/3rds of a stop is 2^15 - 2^14 * 2/3. Sorry, but mathematically, you don't gain that much additional fidelity simply by scaling your image down. DXOMark is "fiddling"