Gradient Blur

In the versions of Adobe Photoshop before CS, it was difficult if not impossible to get a true depth of field effect, where the sharpness of the image changes gradually. It never seemed to work exactly right, unless you manually painted in all of the blurriness, which was usually much more trouble than it was worth.

Well, Photoshop CS makes it all much easier, by controlling the amount of blur applied to an image by using an alpha channel. While this is a quick start on how to get going with the tool, you'll find that there are many possibilities for this new feature from here.

  1. 1. Step 1

    For the purpose of this example, I simply made a thin white rectangle similar to the one at left.

    I made it by creating a new image with whatever background color you want to use. Using the rectangular marquee tool (default shortcut: M), drag out the shape, and pressing Alt+Backspace to fill the rectangle with the foreground color in your color picker. This was all done on the background layer.

  2. 2.

    Next, I created a new alpha channel by clicking the New Channel icon ('New Channel' Icon) in the channels palette.

    Step 2

    By default, the channel is black, but we need to add a gradient to it, because that is what the Lens Blur filter will use to tell how much blur to apply to the image.

  3. 2. Step 3

    To add the gradient, I selected the default Black, White gradient by pressing G and then selecting the correct gradient from the drop down box in the status bar.

    Step 3a

    Next, I dragged the gradient from left to right across the image, while holding down Shift, which makes sure the gradient is perfectly horizontal. Now you should have a channel that looks like the one to the left, and a channels palette that looks like the one below:

    Step 3b

  4. 2.

    Now the fun part. Go to Filter-Blur-Lens Blur..., which will make all the magic happen. This feature is only available in CS+, so if you don’t see it, you'll need to upgrade to get this effect.

    There are two important basic settings to this filter. The first is Radius and you will see that about halfway down the right side of the dialog box. This simply controls how much blur will be applied. The next is the Depth Map settings:

    Step 4

    Step 4a

    Makes sure that Source is set to Alpha 1, or whatever channel you placed the gradient onto. Changing the Blur focal distance will set at what point along the gradient should be sharp, for this example, the slider is set at 0. Hit OK and you are done!

Additional Ideas

It’s not a difficult effect to do, but with a little more practice with it and moving it into ImageReady CS, you can get an effect like the one below:

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