Always a fan of the DIY photography website… and this is really cool. Make your own lenses or adapt others the list of ideas is endless. Digital cameras with interchangable lenses make this easy to do and fun.
This is the simplest of lenses an element stuck on the bayonet mount.
Yet with a simple paper aperture disc it can turn out beautiful images.
There is a whole Flickr gallery devoted to them check it out here the Homemade lens pool