The Brush tool can basically be used to draw lines/shapes of any colour on a blank surface or image. Great if you want to give your sister a moustache but does it have any other, more practical users? Well you'll be happy to hear that yes, it does. As you'll find out in this article.

Editing the Brush tool

Basic use

If you select the Brush tool, which you can do my clicking the brush icon in the tools palette or by hitting B on your keyboard, you can simply draw by left-clicking your mouse and dragging it along. If you want to draw a straight line, make sure you're holding shift at the same time.

Brush tool bar

To alter the brush you're using, take your eyes to the top of the window, you'll see a tool bar has appeared. Here, you can edit the brush, changing it's size, style, opacity and flow.

Size

To change the size of the brush you're using, click on the arrow that's next the where it says 'Brush'. This will open a window where you change the brush size with the Master Diameter slider or by inputting a value in the box next to it. You can also change the hardness of the brush in the same window.

Brush type

If you want to change the type of brush you're using, for instance, I have a set of snowflake and music note shaped brushes, you do this here too. To change your brush type, click on the small arrow-shaped button and a list will of brush types will appear.


Select the one you want to use, Photoshop may then pop up a warning making sure you want to change the brush type, click OK if this happens. Why would you want to change the brush type? Well they create different effects. For example, by changing the brush type from Basic Brushes to Dry Medium brushes, we could create a ragged border. For more information on how to do this, take a look at the tutorial:

Learn how to create a simple ragged border in Photoshop


Next along we have Mode where you can change the Blend Mode which affects how the colour you're 'painting' with blends with the layer you're working on. After Mode there's two options that change the Opacity and Flow of your brush.

Opacity and Flow

Opacity will change the transparency of your brush while Flow will alter how much 'paint' the brush puts on to your canvas.

You can alter the percentage of both of entering a figure into the value boxes or by adjusting the slider that appears once you click in them. The smaller the number, the more transparent and less paint will be applied to your image.

Do be careful when adjusting the Flow, however, as if you paint then take your finger off your mouse and begin painting again, you will end up with areas that have 'more paint' on them than others. If you alter the value in the Opacity box, the Flow will always match the value of it, no matter how many times you paint over your image.

Airbrush

Finally, this icon that looks like a pen with a scribble under it is the airbrush symbol. When you have this selected, the tool you're using works as an airbrush which means the longer you keep your mouse button held down, the more of the effect is applied to your shot. It takes some practice but when you get used to using it, the airbrush makes it easier to gradually build an effect. Have a look at Robin Whalley's Dodge & Burn tutorial for a practical example of how the airbrush can be used: Dodge & Burn

Using a Brush with Layer Masks

Layer Masks

Layer masks, which let you see how an adjustment will change your shot without it actually destructively applying the adjustment, can be edited with the Brush tool. For example, you may want to turn a coloured image black & white but still have some of the original colour showing in your final shot. To do this, you apply a black & white adjustment layer then with the Brush tool selected, click in the square shape in your black & white layer then with a black foreground colour, paint over the parts of your image you want to be in colour.

Paint it black

Using the Brush tool to paint on a layer mask in black hides the adjustment you've applied, bringing the original shot back through. If you accidentally paint too much of the original shot back in, switch the foreground colour to white, which you do by hitting the two-headed arrow next to the coloured squares.

Soften the effect

If you don't want to fully remove the effect, use a grey coloured brush as this will, depending on how dark/light the shade is, change the intensity of the effect. You can pick a grey colour by clicking on the foreground colour which then opens up the colour picker.


If you find the effect is still too strong, reduce the opacity of the brush to soften the effect.

You can find out more information about using Layer Masks here:
Understanding Layer Masks

Alternatively, try using the brush tool and layer masks to improve your portraits:
Improve skin in Photoshop

History Brush
 
What's the History Brush?

Photoshop keeps a record of the adjustments/changes you make to an image, which can be viewed in the History Palette (Go to Window>History if you can't see it), and you can use the History Brush to paint back to one of the previous adjustments.

How to use it

You can paint the whole image but the tool's more useful when you have a section of your shot you want to turn back to a previous step while leaving the rest of the photo alone. For example, colour popping where you have a black & white shot where you turn one main point of focus back into colour.

In a nutshell, you open the History Palette and click in the small box to the left of the adjustment you want the parts of the image you're going to paint on to reverse back to. You then select the History Brush and paint, as you would with the Brush Tool, over your image. For a more detailed tutorial on using the history brush, have a look at this: Colour Popping With Photoshop's History Brush.