151. Blur a Background to Create Depth of Field Before You Begin  148 About Sharpness
See Also 149 Sharpen an Image 150 Blur an Image to Remove Noise 153 Soften Selected Details 154 Add Motion to an Image
One good method to make the subject of your image stand out is to blur the background of the image. When you do this, you can draw more attention to the actual subject and eliminate distractions. For example, you might have a picture of your child playing with other children. You can blur all the other children in the photo so that you child stands out. By blurring the background of the image, you create depth of field. Suddenly, all the other surrounding distractions in the image fade into the distance, and the viewer's eyes can concentrate on the subject, the situation, and the moment. The best tool for blurring the background of your image is the Gaussian Blur filter. When you select this filter, you can create a hazy effect by controlling the level of blurring with the Radius value. The higher the Radius value, the hazier your selection will appear. The Radius value indicates the range of the scan, in pixels from each pixel in the currently selected region or layer. If any pixels within that range are dissimilar, the filter will blur them. Because you want to blur only the background of the image, you must preserve the subject. One way to accomplish this is to create a duplicate copy of the Background layer and apply the Gaussian Blur filter to the Background layer only. Then switch to the unblurred copied layer and use the Eraser tool to erase the background portion of the layer, revealing the blurred Background layer.  1. | Create Duplicate Layer
Open the image you want to adjust in the Editor in Standard Edit mode and save it in Photoshop (*.psd) format. If it's not already showing, display the Layers palette by selecting Window, Layers. In the Layers palette, select the Background layer and then choose Layer, Duplicate Layer from the menu bar to duplicate the selected layer.
| 2. | Apply Gaussian Blur Filter
In the Layers palette, select the Background layer once again, and choose Filter, Blur, Gaussian Blur. In the Gaussian Blur dialog box, enable the Preview check box. Select a Radius value representing the extent of how much each pixel in the region is blurred, measured in terms of pixel length. For this technique, you'll want to set Radius quite high (20 pixels or above), to the extent that you almost cannot make out the contents of the current layer.
Click OK to close the dialog box and apply the blur settings to the Background layer. You will not be able to see the effects of the blurring in the image window because the blurred Background layer is beneath the non-blurred copied layer.
TIPS  | You can also use the selection tools to select the part of the layer you want to blur and then delete the selection. See 97 Erase Part of a Layer for more information on removing contents from layers. If you want to erase content from the Background Copy layer that's directly adjacent to your subject matter, you might want to use the Background Eraser tool. Use this tool to carefully follow outside the border separating your subject matter from its surroundings. The Editor judges where the areas of color contrast are and automatically erases the outside half of those contrast zones. Use the Background Eraser to get right up close, and then finish the job for the rest of the image with the Eraser tool (see 162 Remove Unwanted Objects from an Image). |
| 3. | Erase to Blur Background
Click the Eraser tool on the Toolbox. On the Options bar, set the Opacity of the tool to 100%, and from the Presets list, choose a wide, soft brush tip you can easily work with. If Opacity is less than 100%, the copied layer will not be completely erased.
In the Layers palette, select the Background Copy layer. Use the Eraser tool to erase the background areas and reveal the blurred image underneath.
| 4. | View the Result
When you're satisfied with the result, make any other changes you want and save the PSD file. Then resave the result in JPEG or TIFF format, leaving your PSD image with its layers intact so that you can return at a later time to make changes or additions.
I took a photo of a friend in a golf tournament. Because I wanted to make sure that the viewer's attention was focused on her, I blurred everything in the background, including the other two golfers and the golf carts. By blurring everything but her, she becomes the clear focus of the image, and everything else looks like it is in the distance.
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