I'm currently looking at expanding my kit with an (extreme) wide angle lens. My widest lens is a 75mm, and at times I need something a bit wider, so I've been doing some research on the current crop of available W.A. lenses. And yes, my forthcoming trip into Escalante Canyon has *something* to do with this requirement It seems that Schneider and Rodenstock are the only major manufacturers of wide angle lenses at this time, so I've been looking at the specs for their 58/55mm and 47mm lenses (the Rodenstock 45mm will not cover 4x5). My 75mm Grandagon-N has a specified angle of view of 105 degrees. The specs for the 58/55 and 47mm lenses indicate that the angle of view is 110 degrees. Why are the angle of views so similar between the three lenses? I would expect that the 47 would have a much larger angle of view than the 75 - but the difference is only 5 degrees? Or, is angle of view something different than what I'm assuming? I'm planning on getting the 57mm lens, but I'm a bit concerned that the jump between 75mm and 57mm isn't enough to warrant the price tag. Then again, the extra few $100 for the 48mm may just cancel out the deal entirely. I also have a 110mm lens, so I can somewhat image how wide the 57mm would be, and it seems pretty darn wide; certainly much wider than my 75mm. Lastly, for those of you own one of these lenses and use them for B&W work, do you use a center filter? It's certainly a pricey addition to the lens, and one that I would like to avoid. Comments?