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In ImgAlgos::NDArrCalib it is implemented for Epix100a and  Fccd960.  The algorithm is detector-dependent, executing different code depending on whether an Epix or Fccd "Source" is given to the NDArrCalib module.

The difference from algorithm #3 is quite minor; it starts to fill the intensity histogram in a quite narrow range relative to zero, but if the half of statistics is not found in this range it is extended by 1/4 of pixels (see parameter #3 below for initial guess for range of histogram). This iterations are repeated until the half of statistics is in the range, or the number of bins exceeds 10000. 

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1. (4) - algorithm number; 4 stands for this median algorithm,
2. (1) - type of regions for median algorithm; 3 regions (banks/rows/columns) for Epix100a, and 2 regions (banks/rows) for Fccd960:
   

   1. EPIX100A has an option to turn on up to 3 regions for common mode correction, controlled by the bitword parameter #2: bit#1 - common mode for 352x96-pixel 16 banks,  bit#2 - common mode for 96-pixel rows in 16 banks,  bit#3 - common mode for 352-pixel columns in 16 banks

   2. FCCD960 has 2 regions, also selected by parameter #2:  bit#1 - common mode correction for 1x160-pixel rows with stride 2, bit#2 - common mode correction for 480x10-pixel 96*2 supercolumns

3. (30) - initial guess for range of histogram (relative to 0) in ADU (see above description of intensity histogram).  This number can grow in subsequent iterations if half of the statistics is not found in this range.  It should probably start at around 3 sigma of the noise value.
4. (10) - maximal allowed absolute value of the common mode correction in ADU. If = 0 - no-limit is applied directly, indirect limit = 10000ADU (from limit on intensity histogram described above).

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