Closing Preview Saves File, can this be changed to not saving file?

Since my update to Mountain Lion whenever i open an image in Preview and want to edit the file, i either have to make a copy first or risk making the mistake of editing the original.

Previously in Snow Leopard when i clicked close (red cross) it would ask if i wanted to save the changes.

In Mountain Lion it does not. It just saves the changes and if i want to go back to the original i then have to click 'Revert' and choose Last Opened.

I cannot see the benefit here.

This is after i have 'exported' the edited file (previously save as).

Is there a way to change this back to the previous way in Snow Leopard?

If it was not for my Time Capsule i would have lost a lot of original image files by making minor edits and forgetting to revert back to original.