Duplex is a stylistic filter within Color Efex Pro 4 that is used to select and add a color to your image. You can then adjust the blur, contrast, and saturation within the image to get a desired look. Essentially, Duplex creates a Duotone effect that enhances the mood and drama of an image.

There are a number of controls within the Duplex filter that allow us to enhance our image. We will look at the controls in two parts…

First, Color allows you to select a color from within the image using the Eyedropper Tool, or by using the Color Picker to select a specific color value. You can also use the Eyedropper Tool in conjunction with the Color Picker to really fine tune the color application.

The remaining controls allow you to make additional adjustments to the filtered effect.

- Strength* determines how much of the filtered effect is applied to your image. It is set at 70% by default.

- Diffusion* adds a blur to you image which softens it. By default it is set to 70% when the filter is opened.

- Saturation* controls the vibrancy of the colors within the image. The default value is 20%.

- Contrast* controls the overall contrast of the image.

*Moving any of these sliders to the left decreases the specific effect, while moving the sliders to the right will increase the specific effect.

Tip: To emulate the feel of a true Duotone image, try applying the B/W Conversion filter to your image and then stack the Duplex filter over it! You can experiment with different colors to change the mood and feel of the image.