Hi and welcome to the forum, but please add your location to your profile. This is a condition of membership.
On to your question.
YOu need to distinguish commercial and non-commercial photography. If the photo is for your memories, or learning, then I would see no issues with taking a photo of an artwork.
If you intend to sell or publish an image in some way, then you may need to consider copyright. Some works are so frequently reproduced that copyright is effectively extinguished, at least as far as photos are concerned. The Mona Lisa is an obvious example here (though I think that may be out of copyright form an age perspective as well
)
The third category would be where you take an image, not to reproduce the artwork, but to re-interpret it in some way. This could include, to cite some examples I have seen, superimposing an apple on the Mona Lisa's mouth, Adding an event to the background of The Scream or juxtposing an artwork with a sign, or another artwork that alters the meaning of either or both of the originals. You may also wish to highlight some aspect by shooting at an unusual angle. This third group is probably OK, but it would be a good idea to seek permission of the copyright owner before publishing.
Another issue here, is the venue. If the artwork is in private property, then you need to confirm whether it is OK to take the photo in the first place. In this country, Photos are always OK on public land ( I think APEC was exempted), though sometimes others don't realise this & take exception, but on private land, the owner can define the rules. In a gallery setting, there will always be someone to ask. Make sure you do so. If you ask first you are more likely to get an OK, even if the same person would take exception if they caught you taking photos.
