Noise is not the only governing factor; in fact, this is the lesser issue. Our subject is photography; the dynamic range is not limited alone by noise but by detail reproduction as well. Or do you believe, that the dynamnic range of a camera can be increased by aggressive noise reduction?
However, image reduction destroys details. Therefor the decreased noise level is useless, except on clean, textureless surfaces - but that's, what noise reduction software can solve.
Gabor,
Whilst I agree with BJL's excellent explanation on this issue, I think there's another point that needs to be addressed with regard to resolution, which is also related to your points above. The P65+ is undoubtedly capable of greater resolution than the D3X, so one might tend to think that such greater resolution would apply across the whole 'subject-brightness-range' of the scene.
This is not necessarily true. If the scene being photographed has a high SBR (say 15EV), the P65+ will
not deliver better detail than the D3X in the deepest shadows, whatever the print size (assuming equal print size for the comparison, of course). This is what the statement, 'the D3X has better DR than the P65+', actually means in practice.
We must all have observed that image detail is always significantly degraded in the deepest shadows of any scene that actually has deep shadows. It doesn't matter what camera you use, if the scene being photographed has a high SBR, then detail in the deepest shadows will likely be crap, even at base ISO. This is precisely why it's often necessary to bracket exposure and merge to HDR, or, when possible, use fill flash to illuminate the shadows, when the shadows are not too far away.
Another interesting issue that emerges from these DXOmark results is the apparent huge discrepancy between the nominal ISO sensitivities of the P65+ and the real and actual ISO sensitivity, as measured by DXO.
For example, ISO 400 on the P65+ is actually ISO 178. That's a huge discrepancy. Whereas ISO 200 on the D3X is actually ISO 170, a minor discrepancy. Such variance of course complicates the procedures for comparing the DR of these two cameras. Anyone who wishes to do serious comparisons of these two cameras needs to take this issue into consideration. If DXO is right, a big if perhaps, and what could be the subject of another thread. But bear in mind that DXO probably employs highly qualified scientists who know what they are doing. At the same time, they are in the business of marketing their own RAW converter, so their claims should be questioned.
If we assume that DXO is correct with regard to its ISO testing, then anyone comparing the P65+ at ISO 400 with the D3X, should set the D3X at ISO 200. This is not giving an advantage to the D3X. It's simply getting things right. Phase
appears to have lied about their ISO settings. Many other manufacturers also appear to lie. We expect some variance and discrepancies. But more than a whole stop of variance??? Perhaps lying is not the right word. I don't want to start a legal issue. Perhaps there's some other technical issue which DXO is not addressing.
One way or another, this issue should be sorted. ISO is an international standard. It's supposed to mean something specific. We're very short on international standards. They should be adhered to as much as possible.
If we compare the DR of the D3X at ISO 170 with the DR of the P65+ at ISO 178 at the pixel level (in accordance with DXO results), we find that the D3X has a full 3 stops advantage. That's huge and very surprising. I really think that some of you busy professionals who might have access to both a P65+ and a D3X should take the time to check this out.
