IMO, a very self-serving 'opinion' in that piece of work. The author is playing to his audience. Note that lawyers generally give their clients or prospective clients a legal opinion they'll like.
They go on at length about how much skill goes into making a digital reproduction of an artwork, and I can't argue with that, it might indeed. But skill is not what gets you copyright protection. Creativity is.
And creativity is exactly what you do NOT want in making a digital version of an artwork. Instead, the process should be as 'transparent' as possible. Copying is all about making as exact a likeness as possible; a personal touch is in fact what the copier is trying hard to avoid.
In fact, the flaw in their reasoning is quite easily demonstrated in this: how can they even determine WHICH copyright you're infringing? Unless they've only allowed one reproduction of the artwork ever, then multiple copies exist. If they are trying to sue over this supposed subsidiary 'copying' copyright, then they MUST identify which copyright you're infringing - after all, you're not infringing copyright on the original, out-of-copyright work!
Which is why, probably, the individual from the NPG was so interested in where we got the images from. Without that information, a legal case would be impossible.
-Matt (User:Morven)