Are there defining lines within Art ?

My first time at creating a blog so forgive any sort of mistakes i make.
A classic topic with all who are interested in the fields of art, however for my personal interest am intrigued in understanding and researching how acceptable art is in all its forms by the public and how we perceive what art is. For example, for me photography has changed our perception of art. Let's take for example a dance performance piece (it's art we know this) however photographing this and taking this frozen moment and presenting this to the public as an image and therefore as a 'work of art' in itself for me illustrates in one way how transferable art is. This image can then in-turn be reproduced, copied painted on canvas converted again into some sort of 3D installation so and so on.. there are no limits...and this of course without the possibilities the moving image can bring. This is an ongoing trend but has the perception among the public of art changed as just being a painting on wall?