Photoshop Actions
Dark Grungy Effect
Double Sketch Effect Action
Each of these images have original photos followed by manipulation tools in photoshop. The first picture is changed six different times to portray the differences of a grungy effect available in order to darken the contrast of the picture. In the second image, the photo is an original from a camera and then manipulated to a sketch effect twice.
Of these two images, you can see the differences that can occur in photoshop and these are only two of hundreds of different effects you can do in photoshop. I found these pictures on stumbleupon through the website:
http://www.stumbleupon.com/su/33uCuB/creativenerds.co.uk/freebies/70-of-the-best-photoshop-actions-for-enhancing-photos/
This website portrays all kinds of actions you can do within photoshop including distorting color, changing faces (such as how images are distorted in magazines) and brightening images.