Quote Originally Posted by abo.omar View Post
Let me ask you, what is the difference between:
1-When my father took this photo, I was eating.
2-When my father was taking this photo, I was eating.
The difference is the aspect, which is the way that the speaker understands the action of taking the photo. I can explain it very basically like this:

In 1, the past simple shows that the action is a single action.
In 2, the past continuous shows that the action is a progressive action, which took some time to happen.