Required information
The specific information required can vary from one photo to the next. But for most pictures a reader wants to know such information as:
Who is that? (And, in most cases, identify people from left to right unless the action in the photograph demands otherwise.)
Why is this picture in the paper?
What's going on?
When and where was this?
Why does he/she/it/they look that way?
How did this occur?
Simply stated, cutlines should explain the picture so that readers are satisfied with their understanding of the picture. They need not — and should not — tell what the picture has made obvious. It should supply vital information that the picture cannot. For example, a picture can show a football player leaping to catch a pass, but it likely does not show that the result was the winning touchdown. The cutline should give that information.