A man in a blue t-shirt is taking a picture while a woman with an umbrella walks behind him.
A man is taking a picture outdoors while a woman walks behind him.
"A man in a blue t-shirt is taking a picture while a woman with an umbrella walks behind him" is a more detailed rephrase of "a man is taking a picture outdoors while a woman walks behind him."
Man in a blue t-shirt is a type of man, and woman with an umbrella is a type of woman.
taking a picture while a woman with an umbrella walks behind him he should be outdoor.