That's not how it works. The copyright holder (the photographer your case) has exclusive rights to produce works that are 'derivative' of the original. So your Dad would likely be in violation of copyright law without permission of the photographer. Now one could argue your Dad's painting was fair use on the grounds that it was 'transformative'. But given case law as I understand it (IANAL), that would be unlikely to hold up on court. That said practically it seems unlikely the photographer would sue given the likely market for your wedding photo...