Bio-Rad Quantity One 1-D Analysis Software - Manual (Page 197)

Quantity One User Guide
8-6
8.5 Using the Histogram to Distinguish
Colonies
The histogram in the Colony Counting dialog is a graphical representation of the
signal data in the image. You can use the histogram and associated sliders to reduce
the number of incorrectly identified colonies and/or distinguish between white and
blue colonies in the image.
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 intensity or noise in the image. (For information on subtracting
background from entire images, see section 3.10, Whole-Image Background
Subtraction; for information on filtering noise from images, see section 3.11, Filtering
Images.)
If background is being detected as colonies, you can use the histogram and the 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. 8-5. 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.
Background peak
Cutoff mark