 One of the keys to success in using Photoshop is knowing how to make accurate, speedy selections. Photoshop provides many ways to do this and depending on the image it may require using several techniques to make the desired selection. In this tutorial I'll demonstrate just one of those many approaches, using the Background Eraser tool. I should note that this is by no means my favorite way of creating a selection—the Background Eraser is more typically used for such tasks as touching up a finished selection or layer that has pixels left between frizzy long hair. But for some images it can be very useful for the selection process.
Begin by loading your image and then duplicate the background layer by dragging it to the new layer icon.
Select the Background Eraser tool. You can right-click or use the Options bar or Brush palette to choose an eraser brush size. In most cases you'll want a large one.
To erase the background, simply move the Background Eraser around.
The crosshairs in the middle determine the on-screen area that will be affected by the tool. However, what actually is erased, and to what degree, is determined by the Tolerance % value. In my example image, which has a variety of greens in the grass, I'm going to have to adjust the tolerance a bit. It's best to use a regular eraser for vast expanses of background that need to be erased and use the Background Eraser tool when you want to erase close to your foreground subject, which ideally has a distinct color difference from the background (here's where tolerance comes into play).
A higher tolerance will erase pixels that have a higher difference in color range from the sample point of the crosshairs. The difference between the Contiguous and Discontiguous options is quite straightforward. Contiguous will erase everything that is within the color range closest to the crosshairs. If there is something in the way (such as a braid of hair) that breaks up the flow of the closest color range, it won't reach beyond to erase it (even if it is within the reach of the brush circle). For example, below you can see that Contiguous isn't affecting that patch of green on the other side of the girl's braid.
Choose Discontiguous and the eraser will basically jump across the vastly different outside-the-color-range-braid-of-hair to erase the within-range-color of the patch of grass. Try this out for yourself on your image.
I kept going around the outskirts of the subjects in the image. It was no problem overlapping, as shown below, since the reddish-black hair was not within the sampling color range and tolerance value of the crosshairs.
The illustration below indicates a spot that will require the use of the regular Eraser tool, which you can use later, because the erasing process is leaving particles behind and is getting too choppy. Photoshop provides a wide variety of tools, so it's important to understand them all well enough to know when to switch between them.
Here's another example of Discontiguous in action. Note how the tool jumps beyond the off-color range of the picnic basket to get to the in-color sampling range of the grass inside the handle.
Below shows the result of using the Background Eraser tool on my sample image. To sum up, it's pretty accurate for creating a clearly-defined foreground object, as long as you have a distinct background that separates them. When color ranges are too close together you'll get a lot of spilling over and even adjusting the tolerance value might not be sufficient to make this approach the most effective one.
To make a quick selection, choose the Lasso tool (L) and draw a loose selection all the way around the subject. Now switch to the Move tool (V) and nudge up once and then down with your arrow keys on the keyboard. This will close the selection around the subject, as shown below.
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