Sunday Mailbag: Line Art on Own Layer?

Q: You use a line art and color technique for a lot of your work. What method do you use to get the lines on their own layer in Photoshop (assuming you ink and scan rather than create the lines digitally)?

A: For years I used the “multiply” method, which is simply putting your scanned lines, white paper and all, on its own layer and then setting that layer mode to “multiply”. Everything on that layer then gets “multiplied” with what is below it, sort of like printing the linework on a piece of clear acetate. White is inert so it becomes invisible. That works okay but has a lot of limitations especially if you want to work with lines on multiple layers as opposed to just one layer, and ink density with respect to four color printing can then be a headache.

This is the method I have been using for quite some time now. It uses “channels” to duplicate the lines on a totally transparent layer:

1. Scan line art as grayscale image, or convert your linework file to grayscale
2. Create a new blank layer, rename it “Inks”
3. Go to the “Channels” palette (Menubar: “Window>Channels”), there is only one channel called “Gray”
4. At the bottom of the channels palette, click the “dashed circle” icon on the left entitled “Load Channel as Selection”
5. On Menu bar: “Select>Inverse”
6. Go to your “Inks” layer
7. Press “D” on your keyboard to reset swathes so full black is active color
8. Press “Option” + “”Delete” (“Alt + Delete” for Windows) to fill selection with black
9. On background layer, press “Command” + “A” (“Ctrl + A” for Windows) to select and then “Delete” to delete line art on that layer
10. Convert to RGB or CMYK

Using this technique, your line art layer will contain all your lines but the white will be gone, rather than just inert due to the multiply mode. So instead of this:

You get this:

The great thing is that the channels trick also preserves the subtle gray lines and any washes or values you had in the original inks, as the selection of the channel is smart enough to not just select the absolutes but also the transparencies of the image. You can use this trick to create as many layers of line and colored objects as you want and merge them at will to create layered images. The transparent black reacts differently to merging than the “multiplied” black, resulting in lower ink densities. Best of all, by locking the transparent pixels in your “inks” layer (the checkerboard icon next to “Lock”  at the top of your Layers palette) you can easily COLOR the lines without messing up the quality of them or worrying about the color getting anywhere but in the line .

The one caveat here is that you should scan your lines in at a higher resolution for this technique to make sure you do not lose any linework. I do most of my inks at 200% of print size, so that is plenty large if I scan at 300 dpi. If I was inking at 150% or closer to print size, I’d bump up the resolution of my scan to twice print resolution, or say 600 dpi as opposed to 300 dpi.

I am sure this technique has been used by many people, is all over the internet and I am hardly the originator of it, but it was cool nonetheless to “figure it out”.

Thanks to various people for the question. If you have a question you want answered for the mailbag about cartooning, illustration, MAD Magazine, caricature or similar, e-mail me and I’ll try and answer it here!