Paint in Photoshop?
There have been various natural-media painting packages over the years (Corel Painter is the best known), but their developers have assumed you’ll start from scratch or repaint a source image that you don’t want. Photoshop has long had artistic effects that can make a whole image look like an oil painting. In CS5, it gets paint features that let you paint over an image or on a blank canvas, with realistic brushes and paint. Put a layer over your image and you can pick up paint colors from the photo but keep the original undamaged.
If you’re happy with the preset brushes, they live in the brush presets panel, while if you want to change or design your own bristle tips you can open the Brush panel. You’re not just choosing the size and style of the brush since you can choose how much the bristles move while you’re painting and how much the tip changes shape, what texture the bristles have (and whether they’re all different), how much paint is transferred, and even how much paint is on the brush and whether you’ll "run out" of paint and have to reload the color. As you paint, the color you put on the brush mingles with the colors of the original image–you can choose how much of that gets picked up as well as how wet the surface is that you’re painting (whether the ink dries quickly or smears on the wet surface).
You get an extraordinary amount of control with the new paint options. You’ll need a graphics tablet with lots of settings to make the most of them and you’ll need to invest plenty of time in learning how to use the options to get good effects. The feature represents a shift away from image editing towards image manipulation. If a painting-like effect or a partially painted photo is what you want, you can do it all in with this feature, although its appeal may be limited.