I don't know well about the meaning of this sentence. Could you explain it to me?
Impressionist paintings are probably most popular; it is an easily understood art which does not ask the viewer to work hard to understand the imagery. Impressionism is ‘comfortable’ to look at, with its summer scenes and bright colours appealing to the eye. It is important to remember, however, that this new way of painting was challenging to its public not only in the way that it was made but also in what was shown. They had never seen such ‘informal’ paintings before. The edge of the canvas cut off the scene in an arbitrary way, as if snapped with a camera. The subject matter included modernization of the landscape; railways and factories. Never before had these subjects been considered appropriate for artists
What does " The edge of the canvas cut off the scene in an arbitrary way, as if snapped with a camera. " mean? Could you explain it to me?