Application
A portrait is an image that has captured someone doing something or captureing their emotions. The person in the picture can have their facial expresions saying one thing about themn the surroundings or the background sying another, which would change the way you look at the picture.
Richard Avedon |
Diane Arbus |
Walker Evans |
Context
A portrait can be something you take on special occasion or it can be for everyday things such as an ID card or your Facebook profile picture, but with your profile picture you can change it to show the mood your in or even if you don't like it. Old portraits such as he ones above, you cannot change the message it's sending.
Techniques
The techniques used to take a portrait can be very complexed or it could be a simple snap shot. Some of the more complex portraits need techniques like Lighting and a Studio set up, but a snap shot portrait can just be a photographer walking through a park and and asking someone if they could take a portrait of them.