Canaletto's Regatta

Here's an interesting find. There are at least 2 versions, possibly 3, of Canaletto's A Regatta on the Grand Canal (c1740). One is in the National Gallery, London. The second is in the Royal Collection and is currently on display in the Canaletto in Venice exhibition at the Queen's Gallery, Buckingham Palace. (Click the London icon for more details.)
The picture above is an enhanced view of the National Gallery picture. This enhanced graphic is cleaner and more colourful than the Master Scan image of the National Gallery version (© 2003 National Gallery). Is V3 a digitally enhanced copy, a genuine third version or an excellent forgery?