Hey guys I have a Nikon D300 and i'm looking to add a wide angle to my collection. I really want to use conkin filters on it, so that writes off the sigma 12-24 and possibly others. I'll be using it mostly for landscape for my travels over western europe, so maybe a bit of architechture. I don't mind investing more in lenses, and i'm willing to spend up to 1k... so what is the best lense for me? Also, if you recommend a lense could you please also tell me the ring size so I can buy the ring adapter for conkin p series off of ebay and try to shave some time off of the shipping? I'm a complete amateur but i'm passionate about learning, and investing in a hobby that has totally captured me. Thanks for any suggestions! PS: I have googled this question and seen lots of threads already, but hopefully my specific needs makes the answer a little more clear.