There aren’t a lot of things which will still work when used the wrong way ‘round. Airplanes, cutlery, and shoes, for example, all have a preferred direction of use; turning them around, and using them in reverse seldom turns out well. Photographic lenses, or at least some of them, are an exception to this rule. For macro photography, turning some lenses around will actually improve their performance. This can have important consequences for your photos, and your wallet.
