Hungary and Austria are full members of the EEC.
It is one condition of entry into the EEC that the copyright laws set out in the Berne Convention are enacted in law before entry can be granted, with small local variation.
For instance, the French add on the years of WWII to the '70 years after death of owner' rule. How they make it 14 years is beyond me, but I only live here!
A photo, or indeed any image is automatically owned by the creator, [ or his employer if he/she was paid to make it ].
The museum owns diddly squat.
You don't need proof that you had permission in order to claim copyright. Your pics are unique, if you like, your 'work of art', and any artifact you photograph is not copyrightable, since it's not an image! It's possible that you could commit another misdemeanor, like espionage or trespass or criminal assault [ say by flash-photographing an Epileptics Convention! ], but you'd still hold the copyright while lounging in jail!
