Selective Erasing with the Eraser Tools in Photoshop

The eraser tools let you erase portions of an image to the background color, to transparency, or even to the way your image looked earlier in your editing session. There are three eraser tools — the regular Eraser, the Magic Eraser, and the Background Eraser. All three share a tool flyout menu. The eraser tools look like real erasers so you can’t miss them. But just in case you do, press E and then Shift+E to toggle through the three tools. When you erase pixels (which is basically what the eraser tools do), those pixels are gone. Gone. For good. Before using the eraser tools or the Extract command it might be wise to make a backup of your image. You can save the image either as a separate file or as another layer. That way, if things run amuck, you have some insurance.

The Eraser tool
The Eraser tool allows you to erase areas on your image to either the background color or to transparency. Select it, drag through the desired area on your image, and you’re done. If the image isn’t layered and has just a background, you erase to the background color. If the image is on a layer, you erase to transparency. I rate this tool in the same category as the Lasso tool. It’s quick, it’s easy, but it has limited applications. Use it only for minor touchups. The Eraser tool definitely isn’t a tool to use for making accurate selections. The most useful function I find for the Eraser tool is to clean up my channel masks. Set the mode to Block, zoom into your mask, and clean up those black and white pixels.

Here are the options found in the Options bar that control the Eraser tool:
- Mode: Select from Brush, Pencil, and Block. When you select Brush or Pencil you have access to the Brush picker palette on the far left of the Options bar. Use the Brush picker drop-down palette to select from a variety of brush sizes and styles. Block has only one size, a square of 16 x 16 pixels. But because the block size remains constant, if you zoom way in, you can perform some detailed erasing.
- Opacity: Specify a percentage of transparency for the erasure. Opacity settings less than 100 percent only partially erase the pixels. The lower the opacity setting, the less it erases. This option isn’t available for the Block mode.
- Flow: Set a flow rate percentage when using Brush mode. Flow specifies how fast Photoshop applies the erasure and is especially handy when using the Airbrush option.
- Airbrush: Click the button when using Brush mode to turn your brush into an Airbrush. With this option, the longer you hold your mouse button down, the more it will erase.
- Erase to History: This option allows you to erase back to a selected source state or snapshot in the History palette. You can also press Alt (Option on the Mac) to temporarily access the Erase to History option. See Book II, Chapter 4, for more information.
- Brush Palette toggle: Click the toggle button to bring up the full Brushes palette.

The Magic Eraser tool
The Magic Eraser tool works like a combination Eraser and Magic Wand tool. It both selects and erases similarly colored pixels:
- When you click a layer: The Magic Eraser tool erases pixels of a similar color based on a specified range and leaves the area transparent.
- When you click an image that has just a background: The Magic Eraser tool automatically converts the background to a layer and then does the same thing.
- When you click a layer with locked transparency: The Magic Eraser tool erases the pixels and replaces the area with the background color.
The Tolerance value defines the range of colors that Photoshop erases, just like it does with the Magic Wand tool. The value determines how similar a neighboring color has to be to the color that you click. A higher value picks up more colors, whereas a lower value picks up fewer colors. In my example, I set my Tolerance to 8 and clicked in the upper left of my image. Photoshop selected and erased only a limited shade of black due to my lower Tolerance setting. Here are the other options:
- Anti-aliased: Creates a slightly soft edge around the transparent area.
- Contiguous: Selects only similar colors that are adjacent to each other. Deselect this option to delete similar-colored pixels wherever they appear in your image.
- Use All Layers: Samples colors using data from all visible layers, but erases pixels on the active layer only.
- Opacity: Works like it does for the regular Eraser tool.

The Background Eraser tool
The Background Eraser tool is probably the most sophisticated of the eraser-tool lot. It erases away the background from an image and leaves the foreground untouched, in theory anyway. If you’re not careful, the Background Eraser tool will erase the foreground and anything else in its path.

Like the Magic Eraser tool, the Background Eraser tool erases to transparency on a layer. If you drag an image with only a background, Photoshop converts the background into a layer. To use the Magic Eraser tool, you need to carefully keep the crosshair in the center of the cursor, also known as the hot spot, on the background pixels as you drag. Then Photoshop deletes all background pixels under the brush circumference. But, if you touch a foreground pixel with the hot spot, it’s gobbled up as well.

Here’s the rundown on the options, found on the Options bar, for the Background Eraser:
- Brush Presets picker: Provides various settings to customize the size and appearance of your eraser tip. The size and tolerance settings at the bottom are for those using pressure-sensitive drawing tablets. You can base the size and tolerance on the pen pressure or position of the thumbwheel.
- Limits: The Only setting erases similar colors that are adjacent to one another. The Discontiguous setting erases all similarly colored pixels wherever they appear in the image. The Find Edges setting erases contiguous pixels while retaining the sharpness of the edges.
- Tolerance: Works just like the Magic Eraser Tolerance setting.
- Protect Foreground Color: Prevents the erasing of areas that match the foreground color.
- Sampling: Determines what areas should and shouldn’t be erased. The default Continuous setting allows you to sample colors continuously as you drag through the image. The Once setting erases only areas that contain the color that you first clicked. If the background is pretty much one color, you can try this option. The Background Swatch setting erases only the areas containing the background color.