Photoshop 101 - The History Brush Tool
The History Brush Tool allows you to paint and reveal previous states of images. This can be very useful in creating effects.
Revealing previous states of images
If you are familiar with the brush tool and layers this will be simple. I am going to artwork an image of a Kingfisher to bring out the colours of the feathers. The original image was taken by NatureatYourBackyard over on Flickr.
In this example I am going to turn the image black and white and then bring the kingfisher forward in colour. To turn the image black and white go to Image > Adjustments > Channel Mixer. In the bottom right hand corner there is a checkbox called Monochrome. Check this and the image will go black and white.
Open up the History pane by going to Window > History. You will see the last item should be Channel Mixer. Now we are going to use the History Brush Tool to bring the colour forward. Select the History Brush by hitting Y on the keyboard. In the history panel we need to define which History Item we will be using to paint with. Next to each history item is a small box. Click in the box and you will see the history brush icon appear. Now you can paint back what was in that layer.
In the example below you will see I have painted back in the colour for the Kingfisher. I started with a wide brush and used a fine point brush to finish the details and edges of the Kingfisher.