
The Radial Blur filter
... with Barry Huggins
The Radial Blur filter is another highly effective tool for suggesting movement. It simulates a popular effect used in conventional photography when taking pictures with a zoom lens. A relatively slow shutter speed is used, exposing the image as the lens is zoomed through its full focal length.
The result, when successful, displays a focused centre with blurred lines emanating away from the central area -- as if the viewer were looking down a tunnel. The picture of the four-wheel drive vehicle in the desert looks a little static, and we want to create the sense of drama and urgency associated with driving in a challenging environment.
Using Radial Blur will help.
1 Set Levels
For maximum effect, images with strong contrast or lots of color work best. This generates a strong streak effect, which accentuates the sense of motion.
In this example, a high contrast effect is required.
Press Ctrl+L (Win)/ Cmd + L (Mac) to bring up the Levels dialog box,
then increase the contrast by bringing the black and white input markers closer together.
The impact is clear in the foreground, where the heightened definition is perfect for Radial Blur.
2 Prepare the blur layer
Now duplicate the background layer and rename it "Blur."
Activate the duplicate layer and go to Filter > Blur > Radial Blur.
Set the Blur Method to Zoom, Quality to Best, and the Amount to 38.
Move the centre point of the blur by clicking in the location indicated in the Blur Center window. This will place the centre roughly in the middle front of the vehicle.
If you don't get it right first time, just Undo the effect and click again in a slightly different location.
3 Add Unsharp Mask
The chosen Amount setting creates the feel of movement without destroying the clarity of the image, but the effect needs a little sharpening for maximum impact.
Go to Filter > Sharpen > Unsharp Mask and apply the settings shown.
4 Bring the Background Back
Finally, the original background needs to be re-established. Add a layer mask to the Blur layer by clicking on the layer mask icon, second from left at the bottom of the Layers palette.
Adding The Layer Mask
Painting on the mask with black paint reveals the details of the layer below (the sharper details of the original sky and the dunes on the horizon), while white paints the Blur layer back in again.
The mask appears as a thumbnail on the layers palette, but you can check its extent using two easy options:
Optionclick (Mac) or Alt-click (Windows) on the layer mask thumbnail to view only the mask, or
Option-Shift-click/Alt-Shift-click to see it as a colored overlay.
When you've finished painting on the layer mask (see left), the result should look like this.

Also see: our previous article on radial blurs which gives further tips on centering your blur effect
- This article is the exclusive property of O'Reilly Publishing and Ilex Press, Limited. © Copyright 2005 ALL RIGHTS RESERVED. All images are the exclusive property of Barry Huggins. ©Copyright 2005 ALL RIGHTS RESERVED
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