When I draw a thing, I often first draw it rough using Col-Erase™ blue pencil. Then I go over top and make it look NICER using a dark pencil.
I used to remove the blue pencil from the image in Photoshop by selecting the “blue” channel of the RGB scan and turning that into the line art. That was the old way! This is the new way, and it is better!
Look at this drawing. This is what a raw scan usually looks like. See the faint blue lines in there? Ick.
This is what it looks like when I select the blue RGB channel:
It’s pretty effective, but not a critical hit. I can still see faint traces of the blue lines:
Normally I wouldn’t worry about it. I’d just blow ‘em out by increasing the contrast (through the Curves or Levels adjustment). BUT WHY SETTLE FOR THAT?
I don’t know when Photoshop introduced the Black & White adjustment tool, but it’s my new best friend. Let’s make a Black & White adjustment layer above our raw scan.
You’ll get this fun palette popping up:
… but you’ll still see the faint blue lines. They’ll be in black & white, but they’re still very visible. HOLD ON, that’s because we haven’t DONE ANYTHING yet.
CLICK! I select the “Blue Filter" preset:
Now look where those blue lines used to be:
You can even jack the sliders up to make your old blue lines look BRIGHTER, which is no big deal because our goal in the end will be to make that light-grey that used to be my white paper actually look white.
I’ma add a Curves adjustment layer.
Fiddle with the curves til your paper surface is white and your lines look about as good as they can look:
YOU CAN STOP NOW IF THAT’S ALL YOU WANT. Here’s some bonus shizz. I’m going to show you how to make the most useful line art you can have. Go to the Channels palette and command-click (or CTRL-click if you need your instructions to be that specific to your own personal life experience) the RGB channel’s thumbnail:
You’ll get a selection in the shape of your lines. Important : INVERT SELECTION. Don’t “invert” the contents of the selection, use the INVERT SELECTION menu thing or just press command-shift-I. Then make a new layer to accommodate your line art:
Fill the selection with your colour of choice:
Ta-da! You have useful line art. Why is this more useful than simply setting your line art layer to “Multiply?” Well, give it a try and see if you can’t come up with your own reason. Or just trust me. It’s MORE FLEXIBLE.