Cokin filters are oddly old-fashioned looking things. They're always higgledy-piggledy in a cardboard box somewhere in the camera shop, looking like something that's lain gathering dust in a corner since the Second World War. To use them, you fit an equally old-fashioned looking holding frame to the end of your high-tech USM lens then you slide in the filter. I've got a Cokin close-up filter - looks like a monocle for a very long-sighted Cyclops. It's sort of shonky - it vignettes if you zoom in, it has incredibly short depth of field, and it only gives a single point of focus. But that's the magic of it - plus it's only about 1/20th of the price of a decent macro lens.
Yeah, I love it.
