Since time immemorial, artists have taken advantage of whatever means necessary to express themselves. In this digital age, the mixing of photography and painting is simply another means of self expression.
It is well documented that the Flemish painter, Johannes Vermeer, employed the camera obscura as a part of his technique. This camera-like device utilizes a lens to project a well-lit scene onto a frosted glass plate. Vermeer was a master painter and didn't rely on the camera obscura as a creative crutch. My guess is that he was entranced by the luminous image created by the lens. He utilized this unique look and employed it in his paintings. The art viewing public of the time marveled at this unique view of the world. Vermeer (and likely others) kept the camera obscura a well-kept secret in order to protect their technique.
Today, the digital camera file used as an underpainting in Painter is simply an extension of the camera obscura. It can be used as a jumping-off point to explore the synthesis of a new medium. I often refer to this synthesis as "dipping a paintbrush into a photograph". Who's to say that this is creative laziness on less than authentic art? It simply is what it is: the creative freedom to utilize whatever means necessary to express oneself.
There are certainly bad examples available in any form of art. For instance, bad examples of interpreted photographs are around. Unscrupulous individuals will attempt to pawn expressively interpreted photographs as authentic oil paintings. Situations like these can contaminate the waters of forward-looking forms of artistic expression.
The issue of artistic jealousy or protectiveness comes up, as well. Artists invested in traditional media can be antagonistic towards novel approaches that violate their sense of "how it's done". The terms "paintover", "overpainting" and "smudge painting" have a derogatory connotation indicative a protective posture.
As advocates of this emerging medium, the best approach is to brush this negativity aside and forge ahead. I prefer to describe this medium as expressive interpretation. The goal is to interpret the medium of photography into an expressively painted form, utilizing the vocabularies of both. Just as an oil painter expresses oneself through brushstrokes, so does the expressively interpreted photograph.
Personally, I'm long past these points-of-view. The admixture of two formerly incompatible mediums—photography and painting—represents for me an exciting fertile field ripe with possibility. I'm happy to plant my flag here.
-john
Pixels—It's all in how you arrange them.