Step 1: Create an adjustment layer
The first step is to create a new adjustment layer. Using adjustment layers is a good habit to get into, because it allows you to make multiple alterations to your image without damaging the original background layer, and to undo changes without having to re-do every other step of your editing process.
Click on the Layer menu, move the cursor down to New Adjustment Layer, and then select Hue/Saturationâ€¦ A window will appear asking you to name your new layer. You donâ€™t have to, but it will save a lot of confusion if we name this layer â€œOutputâ€. Ensure that the Mode is set to Normal, the Group With Previous Layer box is unchecked and Opacity is at 100 percent, and click OK.
Youâ€™ll be presented with a window containing three sliders, for Hue, Saturation and Lightness. Leaving the other two centred at zero, slide the Saturation control all the way to the left, so the numerical box reads -100. If you have the Preview box checked you should see your image turn to monochrome. Click OK to complete this step.
Step 2: Create another adjustment layer
In the Layers palette on the right of the screen, click on the background layer to activate it, and then click on the Layers menu and select New Adjustment Layer again. You can rename this new layer to â€œFilterâ€. This time though, click on the drop-down arrow of the Mode box and select â€œColorâ€. Apparently thatâ€™s American for colourâ€¦
Click OK and youâ€™ll see the Hue/Saturation/Lightness adjustment window again. Donâ€™t change any settings at this time, just click OK again.