Dxomark "measured" ISO vs Manufacturer ISO

Started Jan 7, 2013 | Discussions thread
jonas ar
Regular MemberPosts: 314
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Re: The undisputed fact is ...
In reply to TrojMacReady, Jan 11, 2013

TrojMacReady wrote:

jonas ar wrote:

TrojMacReady wrote:


Visible image exposure will not be underexposed by the suggested amounts, as also explained by DXOMark in their X100 review for example:

"On the surface this is odd, but perfectly explainable:

What looks odd according to the reference is the following observation:‚Äč a selected ISO 1600 corresponds to a simple ISO 1000. This measured ISO remains constant for selected ISOs 3200 and 6400.

So far as I know Bill Claff and Marianne Oelund have measured the use of variable analog gain in D800 and determined that the gain is constant above ISO1250 or 2000 depending on the meaurements used. However, the DxO measured ISO vs manufactorer ISO is linear all the way to the highest ISO

Why does the curve not flatten?

Cheers,

Jonas

There are 2 types of digital gain as also briefly mentioned and explained by Guillermo here.

The X100 relies on digital gain as applied in the RAW converter or jpeg engine after the fact (curves). The D800 (and many other Exmor cameras AFAIK) rely on digital gain before writing the RAW file by simply mutiplying values. From what I gathered in the posts from Marianne back then, that's the type of digital gain that she detected. Sadly not one mentioned (or detected) and explained by DXOmark.

Thanks for that!

It makes one wonder even more why Nikon an others  implement unnecessary highlight clipping in raw

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