Now we'll make a new adjustment layer to adjust the Threshold of the image. Threshold gets rid of all the shades of gray, leaving only pure black and white. Using an Adjustment layer instead of applying it directly to the image, allows you to make further adjustments later on if needed, without losing any digital information.

For the most accurate preview make sure the view magnification is at 100 percent. From the side menu of the Layers palete choose New Adjustment Layer and for type choose Threshold and click OK. A setting of 128 is the default Threshold level. This number represents shades of gray, 128 being the mid point of the total of 256 shades of gray that are available in this Grayscale image. A higher number for Threshold Level will make the image darker and a lower number will make the image lighter. Adjust the threshold until the line thickness appears correct. My image had a Threshold Level of 118.