Excellent lens, sturdy, perfect images. Was able to get one from a photographer who was thinking of switching to Nikon just for his architectural pictures. He now is going to get he new canon tilt/shift lenses 17&24, much to my pleasure, since I was able to get this new lens for quite a lot less..... I'm very happy:-)!
As a DIY-er I'll wathc the 'products'of people in coming up with designs for fiters, although a certain amount of care does not inhibit 'full range' shooting.