vincentkong.com

If you want people to focus on the subject of a picture, a photographer would mention something related to the depth of field (DOP), which usually means that the subject needs to be sharp while everything else is blurred.  This can usually be accomplished by setting a large aperture e.g. f/2.8.  Sometimes I find my pictures lack this relationship, either because there is a limitation to my camera or I simply just forgot to adjust the aperture.

Fortunately, this effect can be easily accomplished using the lens blur filter in Adobe Photoshop.  I will walk through this using Adobe Photoshop CS3 and a picture of a giraffe which I took during my visit to Metro Zoo.

1. Open the image you want to edit in Photoshop and duplicate the background layer. From the “Window” menu, select “Layers” or press F7.  Right click on “Background” and select “Duplicate Layer…”.  Finally, set the original background layer to invisible by removing the eye.
   

   Duplicate background layer.

2. Click on the “Channels” tab, and click on the “Create new channel” icon at the bottom of the window.  The entire image will become black and a new channel named “Alpha 1″ will be created.  Set the RGB channel to be visible so the image reappears again.
   

   Create new channel.

3. Use whatever tool you please to fill in the shape of the giraffe.  For example I selected to use “Brush Tool” with white foreground color.
   

   In Alpha channel fill in shape of giraffe.

4. Go back to the “Layers” tab, and from the “Filter” menu select “Blur” > “Lens Blur …” to bring up the “Lens Blur” configuration window.  In the “Depth Map” section select “Alpha 1″ from the “Source:” drop down, and check off “Invert”.  In the “Iris” section adjust the “Radius” value to control the strength of the blur.  Click the “OK” button when done.
   

   Set lens blur filter settings.

5. Go back to the “Channels” tab and hide the “Alpha 1″ channel and you have successfully applied the lens blur filter.
   

   Hide Alpha 1 channel.

Before and After Lens Blur Filter

Related posts:

1. Polarize Filter & Macro Lens for My Canon SX10 IS
2. Using Photoshop Filters
3. Creating static IP in Xubuntu 8.10
4. Set Up Windows Mobile with Google Sync
5. Visit to Metro Zoo