You may have heard of a color in art supplies called non-photo blue. People use non-photo blue to draft roughs that they can pen permanent ink lines on to photocopy which will result in a duplicate with only the black lines. You can achieve the same effect with simple gray pencil lead with a little help from Photoshop.
The first thing you need to do is scan your pencil work. I usually scan in color to capture all the subtle gradation of how the microscopic lead fragments land into the paper fibers. Scanning in black and white will lose all those qualities. Of course, a higher resolution scan will yield a more detailed image. 300 dpi usually does more than I need.
Now that we have the scanned pencils we can go ahead and turn them into grayscale. Go to the top menu and navigate Image>Mode>Grayscale.
Now to turn these into blue line pencils go back to the Image menu and go to Image>Mode>Duotone. A window will appear where you can click on the first color swatch to change the color properties.
Now that you’re in the color picker notice the CMYK attribute fields. Set the Magenta, Yellow and Key levels to 0%. Now set the C, for Cyan, somewhere in between 50 and 100 percent. I tend to use 75 right down the middle. You may have to go higher or lower for visibility depending on how soft you draw. Before clicking OK, you can use the dropdown menu to make it Monotone, since we only want Cyan anyway.
Now print out this image in color. If you have very rough pencils, which is usually the case with me, you can draw over the blue lines with erasable pencil for tighter lines to guide your pen.
I was pretty happy with how this drawing turned out so I’m just going to go straight to inking. Once completed you can now take the printed blue lines with the black ink to a Xerox copier.
On the duplicate you will have a black and white copy with all of the non-photo blue gone. Depending on the copier’s sensitivity, you may have to set the copier anywhere between 10 and 50 percent if it picks up a hint of where the blue lines were. Even at 10%, your blacks should still show. All you would need to do is pump up the contrast in Photoshop after a scan to get that “true black”.
Now you have completed inked art without destroying your pencil work and without using a lightbox or tracing paper!