How does the D3 achieve such high ISO?

Started Feb 17, 2008 | Discussions thread
bobn2 Forum Pro • Posts: 69,811
Re: Well, if we look at it this way...

PIXmantra wrote:

PIXmantra wrote:

Let us take a look at something:

Assuming 7.2^2 surface for 1D3 and 8.4^2 for the D3, and assuming
that there are light-collection capabilities are unformely
distributed on the sensels' area, and proportionally equivalent
between each cam's sensels, we then have:

Surface % of D3 to 1D3: 100*(8.4^2/7.2^-1) = 36.11%
Light-gathering % of D3 to 1D3 @ ISO200: 100*(65,600/38,000-1) = 72.63%

So here we have a 36.11% advantage of actual sensel's surface, yet we
have a 72.63% advantage in collected electrons @ ISO200.

This does not seem to be right... Not in my watch.

D3 Electrons per sensel's surface unit @ ISO200: 929.7052
1D3 Electrons per sensel's surface unit @ ISO200: 733.0246

Or, in summary: D3 comes with a boost of sensel's light-gathering
surface of 36.11%, yet it yields a proportionally lower increase of
26.83% of electrons/surface unit (or sensel).

Another way of looking at it.


Two different things, surely.
1) Larger surface area per pixel (36.11%)
2) More efficient microlenses, no gap vs. reduced gap (28%)
Total per pixel gain = 1.36*1.28 = 1.74 = 74% (some rounding errors here)

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