DxOMark's measured ISOs vs. manufacturer ISOs

Started Mar 13, 2013 | Discussions thread
John Sheehy Forum Pro • Posts: 21,603
Re: DxOMark's measured ISOs vs. manufacturer ISOs

Mjankor wrote:

Ok, you seem to be under the impression that DxO's ISO actually means something like the general definition of ISO.

So, two cameras, Camera A which measures DXO ISO of 200, at its claimed ISO 200, and Camera B, which measures DXO ISO 100 at its claimed ISO 200.

What do you think will happen will happen if both cameras photograph the same scene, same shutter speed, iso200, same fstop?

That depends on why the DxO ISO is different.  It could mean no difference at all in SNR, but only a difference in highlight headroom, or it could mean a big difference noise, and a difference in highlight headroom.  The only given is a stop less highlight headroom in the DxO 200 camera.

Read noise is a wild card, in character and quantity, and has nothing directly to do with saturation-based (DxO) ISO, or any kind of ISO.

DxO ISO has no direct relationship to noise; it has nothing to do with noise.    In fact, there is never any direct relationship between ISO and noise amongst cameras, even amongst sensors of the same size.

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