Tutorial: Using Duotone To Add Art To Your Designs

My How-To tutorial this week showed how duotones, when created with the right curves, can combine a full range of values with extra tonal depth. This tutorial will show how Photohop duotone, tritone and quadtone techniques can be stretched even farther to create designs that look like they came right off the letterpress.

The poster above is one I designed and illustrated for a big street party they had in Des Moines a couple years back. It has a raw feel thanks to a few layers of grit and distressed textures, a simple color scheme and sharp transitions throughout. All these graphic design elements are found in another much-loved illustration style: letterpress. You can see some good examples here:

• Hamilton Wood Type Museum
• Yee-Haw Industries
• Poster Offensive

It can be tricky to create an authentic letterpress feel in Photoshop. Using the Color Overlay layer effect works well for laying flat color to flat areas such as text, shapes and line art—but not for continuous-tone images such as photos, which get entirely covered by color. Even if the design uses only text and line art, applying color to every element isn’t a very efficient way to achieve letterpress style. The ideal method would involve Photoshop applying one color to a selected range of values (such as the highlights or shadows), another color to a different range of values, and another and another. That way it could apply a specified ink to not only line are and text but to certain controllable values in photos as well. But does Photoshop have a tool or technique to pull it off…?

Hmmm…did someone say duotone?

THE GRAYSCALE “SKELETON”

Figure 1: A grayscale image resides behind the colors of the poster above.

The poster at the beginning of this article is a quadtone—a duotone with four colors—and Figure 1 shows the grayscale “skeleton” upon which the colors are based. A grayscale image is all you need to execute this technique! In theory, each color is applied to a unique part of the full value range, and in practice this is done in the Duotone Options dialog box. For the sake of learning I have made available the quadtone curves used to create this poster; you can download them here. (4KB, .ado) Here’s how to use them:

Step 1: With your grayscale image open, select Image –> Mode –> Duotone…. The Duotone Options dialog box appears.

Step 2: Click the Load… button and in the pop-up window select the quadtone.ado file. Click Load.

Figure 2: The Duotone Options dialog box, displaying my quadtone information.

That’s all there is to it! Your Duotone Options dialog box will look like the one in Figure 2, and your image will have the same letterpress style and color scheme as my poster. It’s also very easy to change the color scheme: simply click on the color wells to bring up the Color Picker dialog box and choose your own. (Note: If you are unfamiliar with duotones, read my previous How-To article about duotones for a general overview and detailed description of the Duotone Options dialog box.)

UNDERSTANDING VALUES AND CURVES

Figure 3: Full Value Range + Quadtone Inks And Curves = Full Quadtone Color Range.

Figure 3 is the gradient bar at the bottom of the Duotone Options dialog box, and it’s a handy way to see the quadtone’s full color range when it is applied to the full values scale (if you set the image up as a monotone with black ink, the bar will go from white to black). It’s clear enough that the four colors in the quadtone are distributed thusly:

• White on the extreme highlights (0–5%)
• PANTONE 150 C (salmon) in the quartertones and midtones
• PANTONE 180 C (red) in the three-quartertones
• PANTONE Black in the shadows

Figure 4: This gradual color range is representative of traditional quadtones and duotones.

Compared to traditional quadtone ranges (the one depicted in Figure 4 is from one of Photoshop’s presets) our quadtone’s range has much more defined areas of color. On the far left it is white; by the time it reaches 10% it is already completely salmon-colored. The transition from salmon to red happens between the 40% and 60% marks. In contrast, the transition in Figure 4 seems to build throughout the entire value range. The colors are not well-defined, and in fact it’s impossible to know that this actually has four colors in it (in fact, this quadtone uses blue, black, olive and bright purple!). Our quadtone’s gradient bar illustrates the well-defined areas of color used over the full range of grayscale values.

Figure 5: The four curves that dictate ink application in the poster quadtone.

Figure 6: Curves for the traditional quadtone are very different.

Now on to the quadtone’s curves, which is the key to building these areas of color. In Figure 5 I have assembled the curves for all four inks of our poster quadtone; in Figure 6 below it are the curves for the traditional quadtone. Big difference, huh? Figure 5’s curves aren’t even curved lines! They hug the bottom of the grid, then shoot straight up or almost straight up and ride the top. We haven’t seen this since I used it to help convert grayscale images into clean line art. In contrast, the traditional quadtone curves are smooth curves that deliver a percentage of each ink at any given grayscale value. And there’s the difference—to achieve the letterpress style, we cannot mix inks but instead must use one and only one at 100% strength. That is why the curves are either hugging the ground (and outputting zero ink) or riding the top (and outputting 100% ink).

CUSTOMIZING CURVES TO SUIT YOUR IMAGE

To edit the curves, just click the curve thumbnail beside each ink and decide at which point you want that ink to come to the fore. Remember that the inks are “applied” by Photoshop in the order in which they’re stacked in the Duotone Options dialog box, which means you’ll want your highlight or shadow color on the bottom and work your way across the value range as you move up from ink to ink.

One and only one ink will have a curve consisting of a straight line running across the top of the grid. This ink will constitute the color of your “paper” (because that ink will be 100% across the whole document.

It doesn’t matter much how steep your curves are, only that they run 0% or 100% across most of the value range. Fiddling around with the curves may show that, for your particular image, some good details may show up if the color doesn’t reach 100% at some critical juncture, say, around 58% gray. Remember that the Duotone Curve dialog box is not advanced enough to work with curve points that aren’t multiples of ten (see my notes in the recent duotone How-To for more about duotone curve building). Sometimes a curve that doesn’t go from 0% to 100% as fast as possible is the best curve.

I encourage you to load my quadtones.ado file (again, here is the link) and fiddle with the curves. It will really help illustrate what is going on here.

CONCLUSION

Letterpress (or, at least, letterpress that is used and imitated by a variety of contemporary designers) is all about flat fields of pure color. The technique I’ve described here is an easy way to stretch the power of duotones in a unique way to apply color in much the same way.