This article looks at two methods for creating duotones in Photoshop. But first, what is a duotone?
Think of a duotone and you’ll imagine an image composed of two distinct hues. Easy so far. But a typical printing-press duotone uses black ink and another color, the net result being a photo that is monochrome by many people’s definition. No black appears in the final image unless the initial grayscale image was clipped, which photographers generally try to avoid.
This photo uses two distinct blue-cyan hues laid over the original black (using a gradient map), but it’d qualify as monochrome in most circles.
A sepia image often comes from a duotone process, yet many people think of sepia pictures as monochrome.
Indeed, they are monochrome in the end but try producing a sepia effect in Photoshop using a single brown color. You’ll notice it tends to look flat. You can try some wild curves adjustments, but you really need black or dark gray in there to give contrast.
Using duotone mode to create two sepia photos. The top half is duotone with a mixture of dark gray (near black) and dark brown. The bottom half is what you get with dark brown only – monotone.
For our purposes
We’ll look briefly at the classic black + one color method of creating duotones, not least because that blend tends to create more tasteful results. But I’ll also show you how to produce two-color images in Photoshop CC using two methods: duotone mode and gradient maps.
Method 1: duotone mode
To access Photoshop CC’s duotone mode, you first need an 8-bit grayscale image. But before you convert to grayscale, you might want to do a normal black & white conversion. That way, you can use the color sliders to get the best starting point before shedding data.
The process of creating a classic duotone in this way is described well in another article. Either pick one of the many presets available in Photoshop or choose your own color combo. Then adjust the contrast in the two “inks” as desired using the built-in curves adjustments. Technically, this produces a duotone, even if it’s monochromatic by some definitions.
A two-ink duotone photo that is nevertheless monochromatic in appearance. Only by clipping the original grayscale image can you get true black into the photo.
Tip: in order for your second color (or “ink”) to be the one that imbues the image, you need the first “color” to be neutral (i.e. the default black or dark gray). Otherwise, the two colors blend. To achieve two distinct colors, there’s more to do.
Two distinct colors in Duotone Mode
It is possible to produce a two-color image in Photoshop’s duotone mode. Let’s say you have two colors selected (e.g. black and orange) and you want to make shadows blue. This is what you’d do next:
- Click on “Overprint Colors” to open a dialogue box.
- Click inside the color square next to “1 + 2” to open the color picker.
- Move the picker around and choose a blue, observing its effect on the image in real-time.
- Close “Color Picker” and “Overprint Colors” boxes.
- You’re done! Convert back to RGB for conventional web or printing use.
By clicking on “overprint colors” in duotone mode you can lay a second distinct hue over your darker tones. In this instance, I’ve chosen dark green.
Method 2: gradient maps
Like duotone mode in Photoshop CC, there are many gradient map presets you can try out. Some of these use a single hue or multiple hues, so they might be monochrome, tritone or quadtone in some cases. But a classic two-color gradient map will give you a duotone result with discrete colors.
Using a normal blend mode with a gradient map produces a two-color image without black. There’s a distinct lack of contrast, though this varies depending on the colors chosen.
The method for creating a duotone using gradient maps is here:
- Open a black & white adjustment layer (don’t do anything with it yet).
- Open a gradient map adjustment layer and set a “contrast” blend mode (e.g. overlay, soft light, hard light, etc).
- Click on the gradient to edit its colors.
- Double-click on the lower left and right sliders to open the color picker and select your shadow and highlight colors. A single click on either slider produces a slider in the center, which you can move if you want to alter the transition point between colors.
- Adjust color sliders on the black and white layer if you want to selectively darken or lighten parts of the image.
- Adjust opacity on the gradient map layer to taste.
- Flatten layers.
You’ll bring the contrast of the original image back in by selecting an overlay, soft light, hard light or color blend mode.
When you’re going for a subtle duotone with off-black and off-white colors, you can skip the black and white layer. Just use a gradient map layer with a normal blend mode. Note, however, that this precludes the possibility of reducing opacity (which brings color back in) or selectively adjusting different tones. The extra B&W layer adds versatility.
The normal blend mode also looks pop-arty if you choose bold colors, so it’s good for creating graphic posters or flyer pictures. In this mode, it’s worth bearing in mind when picking colors that a color from low down and one from high up on the picker graph gives more contrast. The nearer the two hues are to each other in terms of “picker height,” the less contrast you’ll have in terms of brightness. Other blend modes add contrast, so this only applies to “normal.”
Another gradient-map duotone using a “normal” blend mode. Blue and orange are complementary colors (approx). Photo: Pixabay
Of course, if your shadows and highlights are so close to black and white that their hues are hard to detect, you’re effectively back to creating monochromes. The semantics don’t matter provided you’re not entering duotone photo competitions with pictures that look mono.
Compressing the tonal range
When using the color picker to select your shadow and highlight colors, any hue you pick above the base or below the top of the graph compresses the tonal range (or dynamic range) of the photo. At least, that is the case if you perform a separate edit or use an adjustment layer with a normal blend mode.
If you’re going for a graphic image with two bold colors, the tonal range is almost immaterial. You can let it fall where it may. But with mono images and subtle duotones, dynamic range is more important. We’re always taught to aim for a full tonal range in our photos so that the data goes end to end on a histogram, but actually compressed data sometimes looks good. It gives online photos more of a print feel in the absence of deep shadows and dazzling highlights. Try it!
The hard left of the color picker goes from pure black to white, bottom to top. The same principle applies to colors. They go from pure black to full saturation. In this instance, I’ve compressed the tonal range of a black and white photo by 5%, lifting shadows slightly and subduing highlights.
Just as you can compress the tonal range of an image using curves or levels, so you can using gradient maps and the color picker. You could do similar in duotone mode by adjusting the endpoints of the built-in curves so that the curve is less steep. Conversely, making curves steeper increases contrast and eventually clips shadows and highlights.
What I did in the above picture using the color picker is the same as doing this in curves. Selecting two duotone colors using a normal blend mode will also compress the tonal range unless you choose the most saturated hue and black. (The baseline of the color picker is always pure black.)
Choosing colors
If you’re looking for colors that go well together, try using the Adobe Color Themes extension in Photoshop CC. You needn’t have an image open to experiment with it. Set your background and foreground colors via the extension in the tools palette, and they’ll automatically transfer over to a gradient map when you open one. Complementary colors are perfect for duotones.
With this photo, I’ve set complementary foreground and background colors in Photoshop CC using the Adobe Color Themes extension. Then I’ve opened a gradient map, which applies the two colors automatically.
There are several websites dedicated to finding colors that work well together, including Adobe Color. These typically include the hex numbers, which you can copy and paste into the Photoshop color picker to reproduce the exact same hues.
Final thought
In times past, a duotone was used as a cheaper alternative to color halftone printing. Today, you could figuratively think of it as a more expensive alternative to black and white. I wouldn’t suggest it’s better (of course it is not), but it’s another way to convey mood. Sometimes you can hint at the color that was in the original photo. Or, you can just make some far-out pop art. There are many possibilities.
