To find out who the copyright owner of an image is, have a look at the image itself or at the work in which it is included.
A photo of a young man. The artist and copyright owner is Robyn Smith.
Details of the artist and the copyright owner, which may or may not be the same person, will generally be set out near the image.
Have a look at this example (.doc 25 kB) of an email or letter asking permission to use an image that has been created by someone else: