Photoshop's Sketch> Stamp filter can do a decent job
of replicating a rubber stamp's unevenness. But sometime
you might want to have a bit more control over the look. Using
several filters in combination gives you a lot of options.
I used a couple of Photoshop's custom shapes and some
simple text to create a "stamp." I used black in
order to appropriately apply filters (we'll change the
color at the end), and I've merged my layers into a single
layer. (The image is not flattened; the artwork remains on a
separate layer with a transparent background.)
NOTE: This artwork measures approximately 470x320 pixels. The
settings used in the following steps are appropriate for this
size. When applying this technique, you can either work at this
approximate size and scale the final product or adjust the settings
for the size of your artwork.
Using the Sketch> Stamp filter with settings of Light/Dark
Balance: 17, Smoothness: 8 gives this result:
Let's undo this and work through some "customized" stamp
making. I'll start with the Artistic> Sponge filter,
using settings of Brush Size: 2, Definition: 12, and Smoothness:
Next, it's the Sketch> Photocopy filter, with Detail:
10 and Darkness: 50.
A one-pixel Gaussian Blur follows:
Let's add a Smart Blur. This particular step will make
it appear that not only is the stamp old, but somebody's
been watering down the ink. (It is, of course, optional.) The
settings used are Radius: 0.6, Threshold: 0.1, Quality: High,
Mode: Edge Only.
Immediately go to Edit> Fade Smart Blur. The Fade command
is available only immediately after applying a filter or adjustment.
If you so much as use the Save command beforehand, Fade is not
available. I reduced the opacity of the Smart Blur filter's
impact to 26%.
To add some color, use a Hue/Saturation adjustment layer. I
checked the Colorize box, set the Hue to 360 degrees, the Saturation
to 63, and the Lightness to 41.
To finish things off, I pasted the stamp into my "passport"
and used the Layer Style dialog box's Blend If sliders to let
the background show through and to break up the stamp even more.
There are most certainly endless variations on this technique.
Different settings, different filters, whatever suits your fancy.
Like most tricks and techniques, it's good to experiment
and modify the steps to suit your needs and artwork.