When the background behind the calibration target pattern is “busy”, has many edges, or has many circular shapes (as sometimes happens when the target pattern is on a patterned carpet), the automarking can slow down considerably. This is because the automarker needs to study every edge in the background to see if it might be a target. In some cases it will actually mark these “false” targets.
In most cases this slow down or the extra false targets do not cause problems with the calibration. There are two methods for resolving the problem.
The first method is to retake the calibration photographs ensuring that the background is clean and noise free. In the “busy” carpet case, putting down a white sheet or large pieces of paper to cover the whole background around the target sheet(s) would help.
The second method involves changing some values in the program’s Preferences. The idea is to narrow some of the search settings so only the high contrast dot targets are found and not the false targets. The settings to change are: 1) Target Marking - Edge Strength High Threshold: try a higher number - perhaps 0.4 - if it is too high proper targets will get dropped also, 2) Target Marking - Edge Strength Low Threshold Ratio: try a slightly higher number - perhaps 0.2 - if it is too high proper targets will get dropped also, and 3) Camera Calibrator - Ratio of smallest target in image to image size: try a higher number - perhaps 0.01 - if it is too high small targets on the grid (those far from the camera) will be dropped. With some experimentation you can find the parameters that will give quick, error free marking in the calibrator.