I have been trying out various filters for long exposures. The crossed polarizer idea is interesting, but it does not really give the light reduction I am looking for (see the picasa galleries on the right). I am too much of a skinflint to shell out £24 for the B&W ND110 (10 stops of light control) at the moment, but I will be testing a 12 shade welders glass when it arrives from eBay. I have seen some promising results in relation to correcting the colours. The one interesting side effect of this is the wide range infrared effects you can get with the crossed polarisers. I am planning a new worksheet guide to that.