I just purchased a 18-55 Nikkor VR Kit lens for my Mikon D70. Went out yesterday to take some landscape photos and noticed that hey all came back being blurred around the center of focus. I also was using a ring adapter with a polarizing filter. Is it common to have to use a larger number f/stop to have the entire frame in focus? I was shooting at f8 to f16. Did shots with and without the polarizing filter. Any help would be greatly appreciated.

Thanks to Mimi....you can view the images HERE and give me your ideas about what is going on.

I also have a 70-300 Sigma lens and I haven't noticed the blur in such amounts around the edges of this lens. Is that because of the wider view that the 18-55 has?