DP2 Merrill sensor read noise finally measured

Started Sep 5, 2012 | Discussions thread
Aku Ankka
OP Aku Ankka Contributing Member • Posts: 591
Re: Aku, one question I forgot to ask

Raist3d wrote:

What is the methodology you are using for the measurements? Note: I am not questioning the results per se or the like, just want to see what the method was to measure all of this.

That you for your interest. It is always a good idea to ask of the methodology.

  • I got the raw files from docmaas.

  • I decoded them using the x3f_extract tool

  • Using ImageJ, using self made script(s) I used the (simplified) photon transfer curve (PTC) method to find out the the conversiion gain and the read noise (good simple guide on this is on ejmartin's web page). The linear fit was very nice.

  • Regarding above, I used two frames for each exposure to remove pattern noise (and to minimize the influence of slight vignetting in the selected crop areas - heavy vignetting was the only real flaw the the raws)

  • One interesting point was the need to combine the data from r,g and b to make the data distribution sane (this is very important).

  • Of the read noise I got slightly different figures directly from the PTC and using the gain on the masked pixels in the bottom of each frame. At this time I my understanding of the technology doesn't allow me to state with absolute certainty which to trust (but the difference is quite small regardless).

  • I may well forgotten to mention something in this list.

I realize this all is a lot of work, thanks for going through it.

I enjoy doing little measuring excersices like that, so no problem. It was my pleaseure.

I have to thank docmass lots for this patience and co-operation. Without him provinding me the test files nothing would have materialized.

Thanks again.

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Raist3d/Ricardo (Photographer, software dev.)- "You are taking life too seriously if it bugs you in some way that a guy quotes himself in the .sig quote" - Ricardo

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