Graphics Programs Reference
6. Switch to the Blue channel within the filter's dialog box and
adjust Strength and Preserve Details as desired.
Adding Lens Blur
Selectively blurring an image can help your viewer find a focal
point. Photoshop offers a realistic lens blur that also produces
depth-of-field blurring. This allows some objects to be in focus
while others fall out of focus. You can be very specific in regard
to the blurring if you make an accurate alpha channel to serve as
a depth matte. The depth matte defines how far away things are
from the camera. Black areas in the alpha channel are treated as
being the foreground, whereas white areas are
seen as being in the distance.
1. Close any open files, and then open the file
Lens Ch11_Lens Blur.tif from the Chapter 11
An alpha channel has already been added
to the image. It was created using the
Calculations command and Quick Mask
mode (see Chapter 5, “Selection Tools and
Tech n iques” ) .
2. Make sure the RGB composite channel is