This plot shows two QC parameters measuring the 
illumination distribution within IFU FLATs.
Both kind of IFU flats contribute: 
<ul>
<li> IFU health check flats generated from one (VIS) or two (NIR/UVB) raw flats and </li>
<li> IFU master flats generated from five (VIS) or ten (UVB/NIR) raw flats, acquired to calibrate science data.</li>
</ul>