Create a Duotone Look?

Open the image you want to apply the effect to, then go under the Filter menu and choose Camera Raw Filter. When the window appears, click on the HSL/Grayscale icon (it’s the fourth one from the left) beneath the histogram and turn on the Convert to Grayscale checkbox to make your image black and white. Now, click on the Split Toning icon (it’s the fifth one from the left) beneath the histogram. You’re going to input some numbers here, but only in the Shadows section at the bottom of the panel (not in the Highlights section up top, and we’re not going to touch the Balance slider either—leave that in the center at zero). Drag the Shadows Saturation slider over to 20, so you can see the color appear, and then drag the Shadows Hue slider to the duotone color you’d like for your image (I usually choose something between 35 and 42 for a warm brownish tone). That’s all there is to it! The biggest hurdle is a psychological one—having the discipline not to touch the Highlights Hue and Saturation sliders or the Balance slider. Just move those two Shadows sliders, and slowly walk away.