Painting Photos
When you make a painting of a photograph, you’re creating a “derivative work.” Your painting gets copyright, but the underlying photo may also have copyright.
If the photo is an old photo, the copyright may have expired, in which case it would be in the public domain and you are free to paint it. Most photos from 1977 onwards have copyright.
For private use, you may probably be able to paint a photo as “fair use.” However, if you want to display your painting publicly for profit, or sell or license your painting, then that may not be fair use and may be copyright infringement. A prime example of what can happen is the story of the famous Obama Hope poster by Shepard Fairey. For the source image, Mr. Fairey used a photo by Reuters, and when he sold copies, the AP wanted their fair share. His choice not to pay Reuters led to a lawsuit which was settled in the AP’s favor.
You can sell a painting of a recent photo if you first license the photo. To do this, contact the photographer, or use a photo from a microstock agency.