One of the most useful features introduced with Photoshop
CS is the Lens Blur filter. Unfortunately Adobe failed to provide
much in the way of guidance as to how it is to be used.
This short tutorial, shows one example whereby I have used the filter
to replicate a widely used photographic technique called differential
Not long after publishing this tutorial a number of readers emailed me
to ask if it was possible to obtain similar effects to Lens Blur
by using the Gaussian Blur filter in earlier versions of
Photoshop. The answer is NO!. Lens Blur works in an entirely
different way to Gaussian Blur. So before we begin the actual
tutorial it is worth demonstrating the main differences between the
Lens Blur and Gaussian Blur filters.
The following explanation of how Lens Blur works is based on a
demonstration called Hocus Pocus Focus given by Russell Brown of Adobe at
Notice that with the grid patterns Gaussian Blur simply softens
the edges whereas the Lens Blur filter results in a blur effect
that has a more geometric shape or pattern to it. Looking at the section
of the image with the 4 circles (representing highlights of different
sizes) we see that the shape of the blur effect in the Lens Blur
example is that of a Hexagon. More interesting is that fact that with the
largest circle we find that the centre of the Lens Blur example
has remained white whilst Gaussian Blur has become a light grey.
The actual shape of the blur effect is determined by the Iris Shape
chosen by the user although not all images will show this effect to the
same extent as shown above.
Lens Blur in Action
In this example the original image has a strong subject but since the
background clutter is so detracting it fails to make any real statement.
With a bit of forethought I could easily have ensured that the background
was out of focus, but hindsight doesn't fix the problem I now face. Can
the new Photoshop CS Lens Blur filter save the day?
We begin by making a selection of the subject. In the image shown
below I used with the Magic Wand and Polygon Lasso tools.
Make the selection using
whichever tool best suits the image
Choose Lens Blur from the Filter > Blur menu
Once the Lens Blur dialog opens hold down the the Alt
key and click the Reset button (Lens Blur will be set t
the default values)
Choose the Alpha Channel form the Depth Map: Source
drop down menu
Select the Alpha Channel as the
Clicking the area that we want to remain in focus (the statue)
causes the Blur Focal Distance slider to automatically move from
0 to 255 (remember 255 is white).
Next we increase the value of Iris: Radius slider and
watch the background (black area) go out of focus. Adjust blur to
Zooming into image so that we can view the subject and background
at the same time enables us to determine the Noise Amount that
needs to be added to the image so that the blurred area doesn't look
The Radius slider located within the Iris section of the
Lens Blur panel allows us to adjust the amount of blur applied to
the image. In this example a value of 0 results in no blur and a
value of 255 is maximum blur.
Adjust the Blur Focal Distance,
Radius and Noise Amount for effect
There is much more to Lens Blur than I've shown in this
tutorial e.g. the use of a black to white Gradient in lieu of the
selection can be used to represent the effect of depth of field.