Step 02: Making the Sketch Blue

Before we go any further, let's learn a little about how computers think about color. Although light exists in a broad spectrum, human eyes can only see a limited range, and they compress the visible spectrum down into three primary colors. So, when we designed printers, computers, and monitors, we only worried about reproducing a color to look the same to our eyes, and not about reproducing colors in their true nature.

There are two basic ways of reproducing color. One way, used by light-based systems such as monitors and projectors, deals directly with the three true primary colors: red, green, and blue. Under this method, light is projected onto or from something in varying shades of these three colors. Where no light is seen, we see black. Where all three colors shine at their full brightness, we see white. In Photoshop, this is called "RGB Color". This color system also goes by the name of Additive Colors, as the more color you put in the brighter the resulting color is.

Another way of reproducing full color is used by printers and inks, where we start with something white (like a sheet of paper), and subtract the primary colors from it. Here, our colors are Cyan (the absence of red), magenta (the absence of green), and yellow (the absence of blue). Due to the nature of ink and light, the combination of cyan, magenta, and blue don't always appear to be true black, so it's common to also have a channel for black ink. In Photoshop, this is called "CMYK Color". Yes, the "K" stands for black, because "B" already stands for blue. If you use this method, Photoshop will be thinking of your colors in these four channels, but of course it will still be translating them to RGB for your monitor. This color system also goes by the name of Subtractive Colors, as the more color you put in the darker the resulting color is.

Keep in mind that RGB color is best for viewing graphics on a computer monitor while CMYK color is best for creating printed graphics.

Okay, back to our sketch. We want to change the color of the sketch to light blue, so that when we begin creating the line work (which we will do in black) we will not be confused by the sketch. We're going to work in RGB color, so the first thing to do is to make sure it is selected...

1. Click Image on the Menu Bar

2. Click Mode

3. Make sure that RGB Color is selected

Note that "Grayscale" and "CMYK Color" are also in this submenu, as well as other less common methods of color.

 Now let's take a look at working with individual colors within RGB. We first need to get up the Levels editor...

4. Click Image on the Menu Bar
5. Click Adjustments
6. Click Levels
7. The Levels editor window (pictured below) opens

We don't want to make any changes just yet, let's just look right now at how the Levels functions. The "Channel" selector indicates if you are looking at red, green, and blue all at once (RGB, the default) or if you are looking at an individual color (Red, Green, or Blue). Photoshop keeps separate level settings for each of these four channels. The interesting-looking graph below that depicts how common the shades of the selected channel are, ranging from 0 (dark) on the left, to 255 (bright) on the right. Since a sketch is white paper with some gray marks, the graph should show the levels clumped up towards the right, as in the screenshot above. Note that some scanners will scan paper as light, light gray, and not true white, in which case the clump will not be up against the very edge but will be shifted to the left.

The main controls in this panel are the three arrows under the graph (see Image 1 below), and the two arrows under the gradient below them (see Image 2 below). The input arrows define where on the scale black, white, and 50% gray are. The output arrows define how white the brightest white can be, and how dark the darkest dark can be. A good example of their usefulness is if you do have a scanner that sees paper as light gray, you can move the rightmost input arrow to the left of the large clump on the graph. This will tell Photoshop that you want to lighten the image so that this clump (the paper) will be true white.

Image 1

Image 2

If you have changed the levels in a way (and you should NOT have, but if you did...), hit "Cancel" and then get the levels editor back up again. We're going to use the levels editor to turn the sketch a light blue. We do this because the dark colored sketch can obscure some of the details of the black ink, and dark smudges cannot slip by as easy if they don't blend in with the sketch color.

 Here's how to make him blue...

8. If it is not already up, activate the Levels editor
9. Next to Channel, select Blue
10. We want to make it so that blue is all light, so grab the dark output arrow (this is the one under the gradient bar all the way to the left under the black section) and drag it as far to the right as it will go
11. Note that the gray lines in your sketch should turn a deep blue

She should now be blue! This happened because there is now as much blue light in the dark lines as there is in the white paper. If that makes no sense to you, don't worry about. At this point we are happy to have her blue.

We can fine-tune her now to get him to a shade of blue you are comfortable working with...

12. Change the Channel from Blue to Green
13. Notice that the dark output arrow we were working with a moment ago has now returned to the left side - this is because we are no longer working with blue but are now working with green
14. Grab the dark output arrow (the same one we dragged around when working with blue) and drag it about halfway to the right
15. Click OK

Note that the blue lines should turn even lighter, and start to look sort of like they were drawn with a blue pencil. If it's still too dark for your taste, you can drag it farther up, and even drag the red dark output up some. It should look something like the image above. There are other ways, even easier ways, to get the sketch blue, but it will help a lot if you familiarize yourself with the Levels editor, which can be very useful at other steps in the process, or even to do things like brighten up a final picture that is too dark. Keep in mind that your version does not have to exactly match the one above - you just want him a color other than black so that you can see the lines when you begin drawing him in.

At this point she is still a JPG file, and while that file format is great for many things, it just does not work well for all the things we want to do to Catgirl. Let's take a moment to save her in the Photoshop file format...

16. Click File then click Save As...
17. Be sure the filename is Cartoon
18. In the Format box click the drop-down arrow and change the setting to Photoshop (*.PSD, *.PSS) (this is the first option in the list)
    
19. Click Save

From this point on to save your Catgirl file you will simply have to click File then Save.

Save your Cartoon file!