Photoshop Effects: Creative Focus with Lens Blur

Step 7: Select The RGB Channel And Then Switch Back To The Layers Palette

Still in the Channels palette, click directly on the RGB channel at the top to actually select it rather than simply making it visible. This will turn off the alpha channel at the same time, and we'll see our image once again as we normally would in the document window:

Once you've selected the RGB channel, switch back to the Layers palette and make sure that "Layer 1" is currently selected. Just as with channels, the currently selected layer is highlighted in blue. Click on "Layer 1" to select it if it isn't already selected.

Step 8: Apply The Lens Blur Filter

We're ready to blur our image with the Lens Blur filter. To do that, go up to the Filter menu at the top of the screen, choose Blur, and then choose Lens Blur, which brings up Photoshop's rather large Lens Blur filter dialog box, with a large preview area for the image on the left and a column of options on the right. As I mentioned at the beginning of this tutorial, we won't be covering all of these options since there's only a few you really need to know about, and one of these options you need to know about is how to select the depth map we just created. At the top of the options column on the right, just below the "Preview" options where you can select from a faster preview or a more accurate preview depending on how powerful of a computer you have, you'll see the words Depth Map along with a Source option. This is where we select our alpha channel to use as the depth map. To do that, click on the down-pointing arrow to the right of the word "None" and choose Alpha 1 from the list:

By default, the Lens Blur filter will use the alpha channel in exactly the opposite way from what we wanted. The areas in the image where the alpha channel was filled with black will have no blurring applied to them while areas painted on with white will have blurring applied. That's not what we wanted. Fortunately, all we need to do to fix that is click inside the checkbox to the left of the word Invert to select that option, which tells Photoshop to treat our alpha channel the way we expected, blurring out the black areas, applying no blurring to white areas, and reducing the amount of blurring over gray areas:

To fine-tune the amount of blurring being applied to the image overall, simply adjust the Radius value by dragging its slider bar left or right, which is exactly what we would do if we were using the standard Gaussian Blur filter. Increasing the Radius value increases the amount of blurring, and decreasing the value reduces the blur amount. I'm going to set mine to about 10. You may want to set yours to a different amount depending on your image and the effect you're going for:

When you're happy with the results, click OK in the top right corner to exit out of the Lens Blur dialog box, and you're done!

Here, once again, is my original image for comparison:

And here, after creating my depth map, selecting it in the Lens Blur filter and adjusting the overall blurring amount in the image with the Radius value, is my final result, with much more attention now being placed on the woman's eyes:

And there we have it! As I said, once you've used the Lens Blur filter a few times, there's no telling how many creative and imaginative uses you'll come up with for it!

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