How To Use The Photoshop Background Eraser Tool

01
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Before You Start Using The Background Eraser Tool

An image of fighter jets is on the left and an image from the window seat of a plane is on the right.
The plan is simple, The jets fly by my window seat.

The Background Eraser Tool in Photoshop is an extremely useful tool. The pros use it to isolate fine detail , like hair, in photos but it can be used for more general purposes. Still, there are a couple of things you need to know before you start merrily erasing backgrounds.

  • It is a "destructive" editing tool. The changes you make are applied to the original image , even it is a Smart Object, and once a background is gone .... it is gone. Always work with a copy of the original image or duplicate the background layer and work on the duplicate.
  • Try having the background of the image to be erased as close to a solid colour as possible. This tool is a brush and it will sample colour within the brush boundaries.
  • Get familiar with making a brush larger or smaller to "paint over" large and very small areas. The keyboard command for a larger brush is the ]-key and for a smaller brush, press the [-key.
  • If you make a mistake , press Command/Ctrl-Z to Undo or open the History panel - Window>History - to go back in time. If you really mess up, delete the copied layer and start over.

Updated by Tom Green

02
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The Background Eraser Tool Options Explained.

The Erase background tool is selected and the Limits pop down in the Options bar shows the three choices.
Precisely removing a background starts with careful choices in the Tool Options bar. Jets image from Getty Images

 When you select the Background Eraser Tool the Options change. Let's examine them:

  • Brush : Set the Brush Size, Hardness and Spacing options here. try keeping the Hardness around 0 to have a nicely feathered edge.Smashing Magazine has an excellent article  explaining the Brush settings.
  • Sample Options: The three eyedroppers do different things. The first one is Continuous Sampling.That means any colour under the crosshair in the brush will be turned transparent. Sample Once will sample a colour you click and will remove only that colour until you release the mouse. Sample Background Swatch will make whatebver colour you click the Background colour and, as you paint, only that colour will be removed.
  • The Limits has three choices in the pop down. The first is Discontiguous which means the brush will erase any of the colour being painted over that the brush finds. Contiguous is great for fine detail because it will remove the sampled colour but any colours not matching are ignored. This is ideal for hair. Find Edges will stop the colour removal at the edges of a sample area. Again, this great for fine detail work.
  • Tolerance: This usually defaults to a value of 30. What it means is the higher the tolerance, the more of the surrounding hues and colours will be removed.
  • Protect Foreground Colour: If you look at the above image, you will see the jets have a bit of blue in them and I don't want to accidentally have that blue removed. To do this, double click the Foreground colour chip and sample a colour you wish to protect.

03
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How To Erase A Background With The Background Eraser Tool

The background behind the jets has been erased.
Take your tuime, pay attention to deatil and do a lot of zooming and brush sizing to get the final result just right. Jets image Getty Images

To start this project I opened an image of the jets and another shot out of the window of a flight I was on. The plan is to make it look like then jets are zooming past my window.

To start I opened the jets image, selected the Move Tool and dragged the jets image onto my window seat image. I then scaled the jets down to fit the upper left corner of the image.

I then selected the Jets layer and used these settings for the Erase Background tool. (If you can't find it, press the E key.):

  • Brush Size: 160 pixels
  • Hardness: 0
  • Sample Once option chosen.
  • Limit: Contiguous
  • Tolerance: 47%
  • Foreground Colour Protected.

 Fom there it was simple matter of erasing the blue sky. I also zoomed in on the planes and reduced the brush size to get into the small spaces. Keep in mind, that every time you release the mouse, you will need to  resample the colour to be removed.Also the crosshair is your best friend. I ran it along the edges of the jets to keep the edges sharp.

It may take a little time experimenting with the background eraser tool options before you can achieve results this quickly, but with a little practice, I'm sure you'll start to see the power of this amazing tool.