How do i fall back from ios7 to previous os level.

This new version is really a bad idea. The more i use it the more irritating it is. I 'm quite close to discarding the machine if i have to endure these exploding zooms and wasted space around my folders. Lack of contrast in monochrome displays is hard to read. I will be happy to revert to latest pre-ios7 level and suffer no more "improvements" thank you very much.