Along with resolution, the threshold is the most important setting you need to choose when scanning a drawing for raster to vector conversion. Choosing the correct threshold can make the difference between raster to vector conversion success and failure.

Choose a threshold that is too low, and parts of your drawing will be missing from the scan.

Choose a threshold that is too high, and parts of your drawing will merge together.

In either event, valuable information is lost and you will not be able to produce a successful conversion.

Below is a video I’ve created that explains what the threshold is and how to set it.

You normally set the threshold at the time of scanning, using your scanner’s scanning software. On our Scanners4CAD large format scanner web site you’ll find information on the thresholding available in the scanning software from the three major large fomat scanner manufacturers:

Nextimage (Contex)
Scanning Master (Graphtec)
ScanWorks (Colortrac)

Free thresholding

If you scan your drawing in greyscale, you can also threshold it within our Scan2CAD raster to vector converter. Thresholding is included in the trial version of Scan2CAD, which provides free and unlimited raster editing.