For the master an expected master bias noise is calculated from the
ron of the raw data, divided by the square root of the number of
frames that were used to create the master bias. Then the population
standard deviation of the pixel values of the master bias is
determined, excluding all pixels that differ more than three times the
expected ron from the median level of the master bias. Details
can be found in the <a href="http://www.eso.org/observing/dfo/quality/FORS2/qc/bias_qc1.html">plot tutorial</a>.

</font><p><font size="2">
<i>DB Name: fors2_bias <br>
TPL.ID: img_cal_bias <br>
Fits header keyword: QC.MBIAS.NOISE <br>
QC1 DB parameter: noise_master
</p></i>