Portrait from Photograph -
Creating a portrait from a photograph can be done exactly as the picture appears or it can be done to emphasize colors, size or simply one element of the photo.
Composite Portrait from Photograph -
Many portraits can include elements from multiple photographs. For example, a person might want to be painted in a different location or beside their best friend. Even if this exact scene does not exist as a photo, each of these elements can be extracted from other photos and reassembled as one, unique, piece.
Special Effects -
There are many ways to enhance photographs. For example, a black and white, charcoal, depiction of a kitten could be created from a photo. This takes some of the emphasis off the many elements and colors in the picture. Then a bit of blue can be added to the piece to highlight the kitten's beautiful, blue eyes.