By Justin Gerard
Please note that this post is geared toward people who are familiar with Photoshop, but still searching for how to best use it to colorize their illustrations. Photoshop Geniuses may find the following a little basic. (Digital ninjas, yetis, warriors, and Kevin Sorbos will find this utterly beneath them)
For the purposes of this post, I created the above monochrome watercolor to colorize. I usually work over full color watercolors, but this should help keep things a bit simpler. (Just know that you can use all these same principles when working over full color work!)
NOW, FIRST OF ALL:
Painting digitally over drawing or a monochrome painting has 2 major pitfalls to avoid:
#1 The Pernicious Photo-tint Look. (Think: old colozied photographs) We don't want this.
#2 The Vile Plastic Over-painted Look. (Think: purple wolf baying the moon airbrushed onto the side of a mobile home) We don't want this either.
The first pitfall suffers from too much information from the original image, while the second suffers from not enough. We want somewhere in between. And thankfully, Photoshop has been built specifically for this. All we have to do is use the right combination of tools within it.
SO LET'S GET STARTED WITH THE BASICS:
To apply color in Photoshop I begin by making a new layer and then selecting a mode for it. In the example below of Little Red "Gonna-Ruin-Your-Day" Riding Hood, I have applied a flat red color to a selected area of her cloak. As I change the layer mode we see how the effect dramatically changes.
As you can see, most of these when used alone, will leave our image looking photo-tinted. (Pitfall #1)
That is where a process of applying a combination of several different layer modes in sequence can be extremely helpful. Consider the following combinations:
Notice how the final effect in all of these offers a more natural looking saturation of colors. Here's why this works:
A surfaces true color is only revealed in the area between the direct light and the shadow.
Certain layer modes saturate more heavily than others. Some darken as they saturate, others lighten.
OKAY JUSTIN, THIS IS STUPID AND YOU'RE STUPID. WHY NOT JUST PAINT WITH NORMAL LAYERS?
Normal layers are great! If you are just getting started, you should work with just these until you feel you understand them. They behave the most predictably and are extremely versatile if you are using brushes with low flow or opacity.
However, if you are adding digital layers over top of a traditionally painted image you will find that eventually you obliterate portions of your original, and the that the final effect is plastic and uneven. (Pitfall #2) To truly take advantage of Photoshop's power, you need to use transparent layer modes.
Photoshop has a dizzying array of options for colorization. What is important is finding what works for you. There is no real right or wrong. It is just whatever you can use to get what's in your head onto the screen.
For me, the majority of my transparent layers are made up of Multiply, Color, Soft Light and Screen. You can do essentially anything with just these four and end up with a solid image.
Multiply Layers tend to darken and add chroma in a very dull application. This is great for slowly building up colors and adding texture and tone to your image. It is very much like working with traditional watercolor. Great for building shadows and toning your image.
Screen layers are essentially the opposite of multiply, these also add color slowly, but they lighten instead of darken. I use these to add direct lighting over the dark layers below. By picking a warm yellow color here I am able to slowly work up a nice natural looking lighting effect to my figure.
Soft Light Layers are bonkers. They have no master, and obey no man. The math that governs them is not fully known to science. What I do know is that when a bright color is used on a soft light layer, it will allow for a very bright saturation of color which does not affect the details beneath it. For instance, I used a bright green color on a soft light layer to really pop the bright greens out from the rest of the image.
Color Dodge Layers scorch out highlights. They are extremely brutal and should be used VERY sparingly. Too much and you are lighting your birthday cake candles with a flamethrower. But when used sparingly, they can help to intensify your brightly lit areas as well as any glints of detail light. I use Color Dodge layers to sharpen highlight areas, add rimlights, and sharpen object profiles against their backgrounds. When alternated with multiply layers it will help push the value range of the image.
Color Layers. Not shown here because I use them so sparingly, but I do use basic color layers to push and pull color in limited areas. The Color layer mode is the classic means of photo-tinting, (and I need not badger you any further with warnings there). Just know that you shouldn't overuse them, but that in limited doses they are excellent. For instance, killing chroma: If an area is too red, I can select a blue color and lightly apply it on a Color Layer and it will pull the red back into check.
Normal Layers. Finally, there is just no escaping at least some opaque work for me when I work like this. But now that we have already established our value range and our colors are fully laid out, we can add details and opaque work that blends rather seamlessly with the rest of our image. I also use it very transparently and often set the layer opacity to less than 50%.
This general sequence offers me solutions to the problems I generally face as I work through an image. Everyone's artistic temperament is a little different, so play around with the different modes in different sequences and see what works best for you.
I hope this was helpful! As always, I take post requests, so if there is something you'd like me to cover please let me know in the comments!