The master bias is averaged along its columns. Then the rms of the
resulting 1-dimensional frame is used to check for the presence of a
bias pattern (predominantly in low gain, 2x2 readout) 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: NA, calculated by the QC script <br>
QC1 DB parameter: pattern
</p></i>