Using the Lens Blur Filter in Photoshop CS

The following summarizes how to use the Lens Blur filter in Photoshop CS.

This filter allows you to blur an image in a manner similar to changing the focus on a lens.

1) First, create a new Alpha channel by clicking on the Create New Channel icon on the lower right of the channels window (note: your image must be in 8 bit mode). You will now have a black channel.

2) Next use the Gradient tool to draw a gradient across the black channel moving from left to right.

3) Now go back to the RGB channel by clicking on the RGB composite in the channels window.

4) Select Filter Blur Lens Blur

The Lens Blur window should open.

5) If you just move the radius around, the entire image will be affected by the blur. This is how you adjust the amount of blur, but not the part of the image that is affected (see items 8&9 below to see how to change the part of the image that is affected).

6) Select Alpha 1 in the Source box under Depth Map and you can now adjust the part of the image that is affected by the blur using the gradient.

7) If you move the radius slider now, you will see that the parts of the image that correspond to the white part of the gradient will blur.

8) If you move the Blur Focal Distance, the blur will move to a different part of the image (the Blur focal distance is changing the level of gray that will blur and this corresponds to the gradient in your Alpha channel). The blur will correspond to the white parts of the gradient in the channel (and where they correspond to the image). You can click Invert and it will apply to the black parts of the image.

9) You can also just click on a part of the image in the preview window and that will be sharp and the blur will be applied to the remainder of the image.