Bio-Rad EXQuest Spot Cutter - Manual (Page 396)

Appendix C. ChemiDoc XRS
C-13
Note: If you are performing experiments that are longer than 5 minutes (e.g.,
chemiluminescence), this should be deselected.
Show Filter Warning - When this checkbox is selected, the software will warn you
to move the filter slider either to chemi or the UV/White position.
C.5.c. Dark Subtraction
At the time of installation a reference dark image file was generated and saved to your
hard drive. The purpose of this file is to reduce dark current noise generated from the
CCD. Dark current noise is typical of all CCDs and is a result of the accumulation of
charge in the absence of light
The default time of the reference dark image is ten minutes. The default reference file
is optimized for ChemiDoc XRS applications. If you select to change the reference
dark image, ensure that the time of the reference dark image is of equal or greater
duration than your typical sample image. When the sample image time is longer than
the reference dark image time the ability to detect very faint samples may be
compromised.
To reset the reference dark image time, select options in the ChemiDoc XRS
acquisition window. Select Reset Referenced.
Fig.C-12. Reset Reference Dark pop-up box
Enter the desired time in seconds. Select OK. You will be prompted to close and re-
open the acquisition window. Place the lens cap on the camera and close the door of
the hood (See ChemiDoc XRS instruction manual). Select OK at the prompt and new
reference dark images of the entered time interval will be taken for each of the five
possible combinations of camera gain and bin settings. These will be retained as the
reference dark images until the time is reset again.