Bio-Rad Quantity One 1-D Analysis Software - Manual (Page 194)

Chapter 8. Colony Counting
8-3
Note: If the border disappears when you release the mouse button after dragging, check
to make sure that the Show Data Area checkbox is checked. This checkbox is
located at the bottom of the dialog.
If the circle is slightly off-center, you can reposition it by positioning the cursor on the
center “target” of the circle. The cursor will change to a multidirectional arrow, and
you can drag the entire circle.
To resize the counting region circle, position the cursor on the outer edge of the circle.
The cursor will change to a bidirectional arrow and you can drag the border in or out.
8.2 Counting the Colonies
After you have positioned the circle, you are ready to detect colonies.
If you are counting plaques, click on the Plaque checkbox. (Because plaques appear
as clear circles on a darker background, this checkbox must be selected for proper
detection.)
Before counting, you may want to adjust the Sensitivity and Averaging parameters
described below.
When you are ready to count, click on the Count button.
Sensitivity
The Sensitivity setting determines the minimum signal intensity in the image that will
be counted as a colony. (This is based on the slope of the signal’s peak.) The higher
the sensitivity, the more colonies will be detected.
If the sensitivity is set too high, background noise will be erroneously detected as
colonies. If the setting is too low, real colonies may be missed.
The default sensitivity setting is 10.00. If the image has faint colonies (e.g., O.D. <
0.05, counts < 2,000), you may want to increase this value to 20.00.