Duotones in Photoshop
Duotones are very cool, but they aren’t used as often as they could be. Personally, I like to use duotones, tritones, etc., to precisely color an image to match the colors I use in a design. Also, another practical use for duotones in Photoshop comes from your clients and their budget. By using duotones in Photoshop, you can specify the colors that make up the image. Using a dark color for ink 1, you are choosing what colors the shadow areas of the images are going to be, and ink 2 determines what color is going to make up the lighter portions of the image. When you create a tritone and a quadtone, it is basically like replacing the CMYK plates with different specific colors. Duotone means two-tone, and tri-tone is three, etc. This is great when you need to keep a design honed in to 2 spot colors to save on printing, or you ned to use a signature Pantone color to make up an image, so that it matches the rest of your design. For example, if you were doing an ad for Sprint and you used their signature yellow to make up the highlight portion of the image.
Here is how it works. First I am going to give you a tip to keep your color image, even though you have to desaturate the image. Right click on the image layer in your layers panel, and make this layer a smart object. This will let you keep your color image, but let you discard the color information in order to use the duotone feature. This feature is only available if you set the mode to grayscale. To do this, go to Image>Mode>Grayscale.
Then, go to Image>Mode>Duotone. From here you have a plethora of options. If you leave the ink 1 setting to black, and click the black color swatch for ink 2, and choose yellow, then you get this sepia look, which looks very natural. You can them any color you want. By default, it makes you choose a Pantone color, but you can click on the color picker option to bring up a box that will let you choose CMYK or RGB values. You can also click on the left-most box next to each color and it brings up a curves option which adjusts the intensity of that particular tone. his helps if you want to make one tone more dominant than the other.
Below is an example of the deep tones and colors that can be achieved by mixing colors. Here, black, yellow, red and a cyan-ish color are mixed into a quadtone.
Also, another aspect is that you can use the presets, which give you different options such as picking a warm gray mixed with a cool gray. This is very handy to achieve certain looks that you want, while adding many options for precise results.