more pixels are better!

Started Dec 14, 2008 | Discussions thread
ejmartin Veteran Member • Posts: 6,274
Re: SNR vs exposure

Graystar wrote:

bobn2 wrote:

That is wrong, there is no evidence supporting the 'DR depends on
pixels size' argument, because it is physically incorrect. What there
is is a lot of anecdotes and poorly framed 'tests'. The physics says
clearly that DR depends on sensor size and efficiency...

Explain why DxO Labs reports that even though the G10 sensor has a
slightly better SNR than the LX3 sensor, the LX3 sensor has one stop
more DR.

There is definitely an error in the ISO calibration of DxO's data for the LX3. My own measurements of G10 vs LX3 at ISO 80 show the following S/N vs exposure:

These are pixel level figures; image S/N involves the S/N at a fixed spatial scale relative to frame height, which involves scaling the pixel S/N ratio by the square root of the MP count. Translated into stops, the G10 curve should be raised by about .25, bringing it closer (but still short of) the LX3 curve. The upshot is that the LX3 has more DR and better S/N throughout the range of exposure levels.

The underlying cause is that the LX3 captures many more photons per unit area than the G10 (.53 e- raw level µ^2 for the LX3 at this ISO; .44 for the G10); and the LX3 has substantially lower read noise (5.6e- per pixel for the LX3; 8.3e- per pixel for the G10).

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