D3 sensor efficiency

Started Nov 18, 2007 | Discussions thread
cpw Regular Member • Posts: 313
Re: Some clarification, please

ejmartin wrote:

I used dcraw with option -D to read out the raw data (the latest
build supports the D3 and D300), and converted to fits format with
the netpbm package; then loaded the result into IRIS, split the CFA
into color channels, selecting small uniform patches to sample mean
and st dev. I actually used an ISO 1600 file for the analysis for
arcane reasons, then scaled up the results to ISO 200. Subtracting
off (in quadrature) a previous measurement of the read noise gave the
photon shot noise in raw levels. The ratio of the mean raw level to
the shot noise squared yields the conversion between electrons and
raw units. After rescaling to ISO 200 I got 13.0 electrons/12-bit
ADU, + - 0.5. Multiplying by 4095 gives the quoted number of
electrons at raw saturation.

Hello Emil,

Very intereting work. As I'm sure you know, pixel-to-pixel nonuniformities can also contribute to your standard deviations. Since I don't know much about the degree of pixel-to-pixel nonuniformity of these sensors, do you have a feel for the size of these nonuniformities, and whether it is so small as to not be a worry?



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