He tried to take a photograph of a beautiful butterfly which was flying past his left ear.
or
He tried to take a photograph of the beautiful butterfly which was flying past his left ear.
Also, is "which was flying past his left ear" a restrictive or non-restrictive clause in this sentence? I feel like it could be presented either way. Can please somebody clarify these 2 points (a/the and restrictive/non-restrictive) in this particular case.
Either is possible in British English. It might be more informative to show the difference in US English because they distinguish more clearly between "that" and "which" than we do.
US English
1. He tried to take a photograph of a beautiful butterfly, which was flying past his left ear.
2. He tried to take a photograph of the beautiful butterfly that was flying past his left ear.
In the first case we are alerted to the existence of the butterfly and then given some information about it.
In the second case "that was flying past his left ear" defines the butterfly that we are talking about. It distinguishes it from other butterflies in the area.
