D3 sensor efficiency

Started Nov 18, 2007 | Discussions thread
Marianne Oelund Veteran Member • Posts: 7,753
Calculating relative stops

ejmartin wrote:

OK, I went back and did a somewhat more thorough job of analyzing
available raw data.

The result: the D3 collects 15.4 electrons per 12-bit raw level at
ISO 200, or about 63,000 electrons at raw saturation for this ISO
(and about 18% better than my initial rough measurement). This is to
be compared with the 1Dmk3, which collects 10.2 electrons/12-bit raw
level at this ISO, or a little over 39,000 electrons at raw

The number of stops advantage is not calculated by taking the square root of the electron count ratio.

For example, if camera A collects 40,000 electrons at a given exposure and camera B collects 20,000, then camera A has a full stop advantage (it will have the same level of shot noise as camera B when collecting 20,000 electrons, which would be at half the exposure, or one stop difference).

The correct calculation of stops of advantage from your above D3 and 1D Mk III data is
(log(63,000/39,000)) log(2) = 0.7 stops.

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