Molecular Devices QPix 420, User Manual

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Chapter 6: Picking Processes
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6. With the Auto Threshold Each Frame check box selected, enter threshold values in the
Low Limit and High Limit fields.
To determine the Low Limit value, clear the Use Auto Thresholding check box and
then drag the slider to the left until some background is clearly detected. Select the
Use Auto Thresholding check box and the Auto Threshold Each Frame check box
again and then enter the value from the Threshold field into the Low Limit field.
To determine the High Limit value, clear the Use Auto Thresholding check box and
then drag the slider to the right until some colonies start to become undetected. Select
the Use Auto Thresholding check box and the Auto Threshold Each Frame check box
again and enter the value from the Threshold field into the High Limit field.
7. Select the Invert Image check box to make dark areas bright and bright areas dark.
Tip: This is most useful when imaging plaques.
8. Select the Subtract Background check box to have the background become nearly black.
9. Select the Display tab.
10. Select the method for viewing the detected colonies in the image.
Click Image Only to display the detected colonies in white with yellow rings and a gray
background. The yellow ring shows the colony detection.
Click Image and Overlay to display the detected colonies in green with yellow rings
and a gray background. The green shows the threshold overlay.
Click Overlay only to display the detected colonies in white with yellow rings and a
black background.
To remove the yellow ring from the detected colonies, deselect the Outline Detected
Features check box.