To perform the conversion, just activate the monochrome module (Section 18.104.22.168, “Monochrome”). You can then simulate a color filter, by dragging the circle above the colors you want to filter. Filter size can be modified via scrolling the mouse wheel.
To perform such conversion we use the color correction module (Section 22.214.171.124, “Color correction”).
Activate the color correction module
Use the bottom slider to set saturation to zero
To perform such conversion we use the color contrast module (Section 126.96.36.199, “Color contrast”).
Activate the color contrast module
Set both steepness sliders to zero
To perform the conversion we use the color zone module (Section 188.8.131.52, “Color zones”).
Activate the color zones module
By default, the active tabbed control is set to “saturation” whereas the “select by” combobox is set to “hue”. This means that color are selected according to their hue (horizontal scale) and you can change for each hue its “saturation” (vertical scale). You simply need to set all points to the minimum of the vertical scale to de-saturate every hue.
But now if you want, you can keep some hues a little bit saturated, so your image will be all black and white but some hue. A classical use for portrait is to keep red hue saturated in order to make the lips standing out.
You can also use one of the available presets that perform black and white conversion, keeping some hues saturated.
To perform the conversion we use the channel mixer module (Section 184.108.40.206, “Channel mixer”).
Activate the channel mixer module
Select the gray output channel
Set the proportion of each color, the sum having to equal 1 if you want to keep your global lightness.