Read Noise from DXOmark "Full SNR" data

Started Oct 25, 2013 | Discussions thread
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DSPographer
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Read Noise from DXOmark "Full SNR" data
Oct 25, 2013

The sensorgen.info site gives read noise data that it derives from a fit to the DXOmark "Full SNR" plot data, but its values are not exactly correct, and sometimes they are significantly different than the correct values. Since I have fit the DXO data and found that their plots exactly match a fit for a model which parameterizes the plot using read noise, saturation capacity, and pixel response non-uniformity I will show here how to correctly perform that fit.

First, to get the data, click the measurements tab on a full review for a camera in their camera sensor database. Next click the "Full SNR" tab and select the linear pushbutton. Now select "view the page source" in your browser. Search for "snrdetail" and you will find a match like the following:

snrdetail.php?appareil=904

Now in Firefox or Chrome, open a tab and enter the web address for the data as follows:

view-source:http://www.dxomark.com/dakdata/graph/snrdetail.php?appareil=904

Except replace the number after "appareil=" with the number you found with your search.

Save the resulting page as "html only" in a php file: I use a name like "Brand-Model.php"

Now you can run my DXOdataFit Matlab function which I will post below. When it asks you to select an snrdetail source file you navigate to the php file you saved. After you are done selecting source files just hit cancel to quit the function.

Or you can run my PlotDXEdataFit Matlab script which calls the DXOdataFit function and makes some plots.

If you don't have Matlab you should be able to adapt my routines to run in an open source equivalent like Octave or SciLab.

Note that the DXO data for ISO values where the full well capacity is below about 1000 e- goes haywire. So, I didn't plot those values in PlotDXEdataFit. This is okay because all sensors so far don't actually have improved sensitivity for such high ISO values anyway. So, you can just expect the read noise is unchanged from the last valid value.

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