Task: Make practical use of channel adjustment to achieve a specific effect.
I chose this landscape image for the exercise, showing a field with track leading to the electricity pylons in the distance.
The default black and white version (below) shows a very flat scene. The pylons are paler in the distance but the tone of the foreground is still quite light.
Therefore using Photoshop I changed the colour version to grey-scale. I then experimented with adjusting the various colour sliders. To my surprise altering the yellow had the greatest effect, even more than the green. Looking back at the coloured scene I can see that although there is a large proportion of grass it has a yellow tinge to it. Reducing the amount of green and yellow has produced a much darker foreground (below). The darker foreground has emphasised the track running across the image from the right and up towards the horizon. The increase in the tone of the grass has meant that the pylons appear fainter and emphasise the depth.