I'm quite keen to practice some macro shots, but I genuinely can't afford to splash out on any macro lenses at the moment (unless someone can't find me something decent for less than £100!). As such I've been browsing on ebay and found these spacer lenses. Do they work? Are they any good? Of course they aren't going to be a suitable substitute for a proper macro lens, but they are cheap and was wondering if they could do the job temporarily.