I did my own noise measurements over uniform patches to calculate the Signal to Noise Ratio (SNR) for several cameras: Canon 5D, 5D2 and 7D, and Pentax K5.
I used the lowest real ISO (ISO100 in Canon and ISO80 for the Pentax), and ISO1600, which is the highest useful ISO value for any RAW shooter on any camera (pushing ISO further means no improvement in SNR).
These plots were obtained:
Since those cameras have different pixelcounts, a fair comparision requires to normalise all SNR values for the same output resolution. I used the Canon 5D as a reference, so the other cameras (with higher pixelcount than the 5D), obtain improved SNR plots:
Looking at this noise response, the following conclusions are clear:
* At ISO1600 the K5 performs like any other modern APS-C in the whole range
* At ISO80, the SNR curve of the K5 is excellent, yielding a very low presence of noise for low exposure values
This means the K5 at ISO80 is a very high dynamic range camera, capable of recording detail in the deep shadows where other cameras fail. Another advantage of this behaviour is the ability to 'recover' detail when the capture was erroneously underexposed.
Calculating the Dynamic Range over the last set of plots, using a 12dB SNR threshold criteria, the following comparable DR figures are obtained: At ISO80, the K5 has almost 2 stops more DR than the Canon 5D Mark II FF camera
. When new FF sensors appear with such a performance, we can start to think about forgetting the need to shoot several times in HDR scenes.
Using FFT in order to try to detect noise reduction applied to RAW data, doesn't provide any evidence of clandestine process:
Complete article (Spanish): http://www.guillermoluijk.com/tutorial/noisedr/