Originally posted by c a sugg 14 stops with the K-5? Really?
I'm not sure if that's possible with B&W film and still have a usable tonal separation.
I don't like the above answer as I think the original post asks a valid question.
As a matter of fact, there is no ISO or DIN standard how to measure dynamic range.
Consider for a moment that the sensor in the K-5 can register either 1 photon or the maximum of photons before it runs over (for equal illumination). Which are 16 million times 40,000 photons. Or 640 billion photons. The ratio of 640 billion : 1 is 2^39 : 1 or 39 stops. So, every dynamic range statement below this theoretic maximum is based on some definition.
DxO defines dynamic range as the ratio of luminosity for bright white and a dark tone where noise approaches the same magnitude as the signal itself; when looking at the image resized to 8 Megapixel. This is the best dynamic range definition up to now.
And yes, according to this definition, the K-5 has 14.1 stops DR. In the same way as a 7D has 11.7 stops DR or about 2 1/2 stops less. This
difference in DR is real and largely independent from an actual definition. The
absolute value however doesn't mean much w/o digging into the definition how DR was defined.
For practical purposes, I would subtract 3 EV from all DxO figures when it comes to decide how much exposure lattitude you can count on. Which means you can still underexpose by 3 stops to preserve full 8 stops of output dynamic range w/o sacrfycing in tonality.
When it comes to camparing with film, you first would have to come up with a good definition of real lab measurement for film DR. My own impression is that DR in a K-5 is on par with medium format film. For B&W, it would depend a lot on the gradation too. But I'd like to see a serious treatment about the question myself. I sometimes see densitometer RMS measurements for film but that can only be a starting point.