User guide

Colony Counting
17-7
Colonies Versus Background Noise
If there is a clear peak on the left end of the colony counting histogram, it is
probably due to background noise in the image. (For information on
subtracting background from entire images, see section 12.9; for information
on filtering noise from images, see section 12.10.)
If this background noise is being detected as colonies, you can use the
histogram and Cutoff slider to correct this.
Drag the Cutoff slider to the right until it is centered on the right edge of the
background peak.
Fig. 17-5. Using the Cutoff slider.
The yellow portion of the bar beneath the histogram marks the range of
image data has been designated as background noise, and is not being
considered for colony counting purposes. The gold portion of the bar marks
white colony data range.
The colony count displayed in the dialog box and on the image should
decrease. On the image, you should also see the incorrectly identified colonies
disappear as you drag the slider.
White and Blue Colonies
If you know you have white and blue colonies in your image, and there are
two clear peaks on the histogram to the right of the background peak, you can
use the histogram to distinguish between these types of colonies.
Background peak
Cutoff mark