I'll give my own personal view based solely on my own feelings.

If the intention is to deceive and purvey an art work as your own when it is someone else's then I feel a wrong has been done. 

If, as your posting today, a photograph has been taken of a piece of art and there is no intention to deceive, then no wrong has been done. In your posting it clearly stated you were taking a photograph of an artwork, therefore with me it falls into the latter category.

My views are probably not strictly in line with copyright law. Today we live in a very litigious society. English law is founded on what a reasonable person would believe. IMO in recent case history weakness has been shown by the judiciary by allowing the law to be tied into knots by people who would challenge the very fabric of the law to win a case, thereby changing the law based on case study to the detriment of more important issues.   

But hey that way lies a deep philosophical discussion on the law, and is it there to benefit society as a whole or the individual. The modern Keynesian view of society is that of the individual, because it promotes economic growth !

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html