Originally posted by JohnBee I would expect both samples to be too close to call at 100%.
Actually, your "case study" already provides two samples being too close to call. I had to try hard to spot the minimal difference. Good job.
My point was that a minimal loss of information is unavoidable at ISO 6400 even with a camera as stunning as the K-5. After all, it's only 1/64 of photons which are <1000 per pixel reaching the sensor (actually, it's about 6000 which ~600 of are detected after the Bayer filter) ... NR may hide most of this. But not all.
I provided an ISO 6400 raw sample early on and it has textured areas (the printing pattern) which start to smear out and the NR can't do anything about it.
I compared a K-x and a D700 (both 12MP) in the lab. The D700 has 1 stop less noise at ISO 1600 (
Falk Lumo: Lumolabs: Sensors of Nikon D700, D5000 and Pentax K-x) and appearantly about equal noise at ISO 12800. However, the noise then looks more smeared for the K-x (D700 has more fine grain noise looking more pleasing) and DxO confirms (by a cross correlation test) that the K-x plays tricks with the raw data beyond ISO 1600. My article contains test patches you can look at. The Pentax tricks may confuse the average tester but not DxO, .. or me
The final call is still out. But for the moment, I have no reason to believe that the quantum efficiency of the 16MP Exmor HD is higher than that of the 12MP one in the K-x. Therefore, the resolution-normalized 18% gray noise measurements will only improve that much. You can't beat the laws of physics.
Where the K-x, and probably K-5 in particular, does excell is read-out noise rather than quantum efficiency. It is probably low enough to make a difference at ISO 100,000+ to challenge the D700. But not below. Where the read-out noise shows off though is dynamic range below ISO 200 where it will probably beat the D700.
Don't misunderstand me: the K-5 has a stunning sensor, esp. wrt DR and as it seems, color rendition.
But it does nothing about the 1 stop difference between APSC and FF in high ISO noise. And the current king in high ISO noise (the D3s) even stays almost 2 stops away ... If the K-5 can narrow
this gap then that would be great
Just don't say K-5 gives FF a run for its money. If you do, you pay with my voice of ratio