D3X vs 5D2 - myth and reality

Started Jan 26, 2009 | Discussions thread
bobn2
bobn2 Forum Pro • Posts: 61,416
Re: D3X vs 5D2 - myth and reality

nikosR wrote:

It's hard for anyone interested to argue with you when you don't
provide any supporting evidence for your claims or explain your
methodology.

Gabor's methodology is realised in RawNalyze. It would be nice, however, if he'd given his figures.

BTW DxO purport to have measured the following max DR values for the
two cameras at their ISO 100 setting (measured before resolution
normalisation):

5DII: Claimed ISO 100, Measured ISO 73, DR 11.16 EV
D3X: Claimed ISO 100, Measured ISO 78, DR 12.84 EV

As Iliah Borg pointed out some time ago, the 'claimed ISO' is the actual ISO, according to the ISO standard. The other one ('measured ISO') is an arbitrary measurement of relative sensor sensitivity, which I like to call 'Index of Sensor Output'.

At ISO 400 setting:

5DII: Claimed ISO 400, Measured ISO 285 (!!), DR 10.92EV
D3X: Claimed ISO 400, Measured ISO 337, DR 11.25EV

The 5DII is measured as having equal DR to the D3x near measured ISO
564 ( 5DII claimed ISO 800!!) with DR about 10.66EV. From then on
(higher than measured ISO 564) the 5DII exhibits slightly better DR.

They say they measure DR from well saturation to S/N=1 (a noise floor
which btw is probably useless from a photographic point of view but
correct from an engineering point of view)

This does kind of triangulate against at least some other evidence. Looking at Roger Clark's compilation of read noise on various cameras, and making the assumption that the D3x has the same read circuitry as the D300, but the sensor has been slowed a stop, the read noise at 100 ISO is 6.6 e- for the D3x and 23.5 e- for the 5DII. If they have around the same FWC, that would give nearly 2 stops DR advantage to the D3x, if the D3x FWC is a bit smaller (Iliah Borg has measured it, but not given the figure, so far as I know) that advantage may be a bit less.
By ISO 800, on the same figures, the 5DII has the advantage, by 3.7 to 4.6.

Any evidence you provide to counter DxO claims should counter the
above DxO findings.

In the end, it's about gathering as much data as possible and correlating the results. There is also the subjective issue which Iliah Borg referred to. Different noise distributions can have different subjective results, apparently obscuring fine detail or giving a 'smooth' result. In the end, if you want quantitative informatio on that, we'd need to have noise distribution graphs and do some perception experiments to see which are 'better'.

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Bob

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