The Photoshop Paintbrush Tool for Photographers
The paintbrush tool in Photoshop is one of the most commonly used tools for retouching photographs. But most users have only a basic understanding of its features. There's more to it than first meets the eye. Or the hand. You have two hands, after all.
The brush tool has options bar controls as well as both a brush presets panel and a brush panel full of even more options. To reach the options bar, all you have to do is activate the brush tool by clicking on it in the toolbox. The brush presets panel can be opened using the Window >> Brush Presets menu command. To reach the full brush panel, you can either use the Window >> Brush menu command or click on the equivalent link icon in on the brush options bar.
But even as I propose to discuss the features of the brush tool photographers should know about but sometimes don't, I contend that you should rarely need to go beyond the options bar controls. Even more, you really don't even need that since most everything has a keyboard shortcut. Clicking on menu commands or panel controls requires the use of your mouse — the same mouse that functions as the paintbrush itself. In order to click on something in a panel with your mouse you have to interrupt your mouse painting which makes it very difficult to concentrate on your painting.
Two of the basic properties of the brush tool are its size and shape. If you're an artist trying to simulate the effects of traditional media and tools, the brush panel and the new mixer brush introduced in Photoshop CS5 are likely already your best friends. As a photographer though the Brush Panel contains way more than you actually need. Bristle tips and natural textures don't have much of a place for touching up dust spots or dodging and burning.
But the brush size is still quite relevant. Thankfully, brush size can easily be controlled with your keyboard. To increase the brush size, use the right-square-bracket key ( ] ). To decrease the size, use the left-square-bracket key ( [ ). Some keyboard shortcuts are difficult to remember but these shouldn't be since the shape of each keystroke resembles an arrow pointing left for decrease or right for increase. With a bit of practice you can easily adjust your brush size while you paint — one hand on your keyboard and the other on your mouse.
You can do the same thing with the hardness of the brush edge too. Rather than stopping to click on the control in the option bar and adjusting the slider for hardness, you can use the equivalent keyboard shortcuts. Simply hold down the Shift key and use the same left or right-square-bracket keys as above to decrease or increase brush hardness. Without the Shift key depressed, these keys change brush size. With it held down, they control hardness. Most photographic paintbrush actions are best done with a modestly soft edged brush to ensure they blend well with the surroundings.
Opacity and Flow can be confusing topics. If you keep the mouse clicked, the maximum density that will result no matter how you paint is controlled by the Opacity setting. A high opacity covers well. A low opacity is relatively transparent so that what is underneath shows. Flow determines how quickly you reach that opacity. If you hold the brush over a given point, it will take longer for the maximum opacity to be reached if the flow is set low, and vice versa. All bets are off though if you release the mouse button and paint over that spot with a new stroke. Each time you do so, the limits are reset. Set the Opacity to 33 percent and paint once and you won't be able to get more than 33 percent no matter the Flow setting. Release the mouse, click and paint again on that spot though and you can now get as high as 66 percent. Do it a third time and 100 percent (or actually 99 percent) is attainable.
As with other brush characteristics, opacity can be controlled in multiple ways. One the one hand you can use your mouse to adjust it from the brush options bar, but if you up for being ambidextrous you can use both hands, one on your mouse as you paint away, and the other on your keyboard. Yes, there are keyboard shortcuts for opacity. Simply press the digit keys 1 through 9 for brush opacity ranging from ten percent to ninety percent in ten percent increments. Since there is no "10" key on a keyboard, the zero key fills in for one hundred percent opacity. Hold down the Shift key as you press the same digit keys and you will adjust the Flow to these same percentages.
To make sure your edits are appropriately subtle, I'd suggest using a low Opacity setting as well as a modest Flow value. The precise settings will vary based on the exact edit you are performing. Keep in mind though that you can always paint more with a lower opacity while undoing changes made with a setting that is too high is much more difficult. If you are painting anything you might later want to undo its best to create a new layer and paint on it to avoid modifying actual image pixels. I'm a big fan of nondestructive editing.
You can also control the blending mode for your brush strokes directly from the brush options bar dropdown box. While this may seem convenient, I usually prefer painting on a layer and adjuting the layer blending mode. There are exceptions for simple edits of course, but most operations that involve blending mode can also benefit from being done nondestructively.
If you own a Wacom or similar tablet, using it to control key brush parameters can make editing particularly easy. Wacom lets you control either opacity or brush size by means of the tablet stylus pressure. Press harder and you increase the selected value. Press more lightly and you decrease it. Painting this way becomes quite intuitive. I've owned a couple of Wacom tablets over the years and love using one. Definitely recommended if you're serious about your Photoshop paintbrush edits.
The paintbrush tool is extraordinarily useful for even modest photo optimization. As a photographer, I'm not much interested in simulating traditional painting techniques, but knowing how to effectively use the basic brush tool should be an essential skill of every Photoshop user, including us photographers.