I feel stupid for asking this and maybe I'm totally off base. I have a Nikkor 18-70mm lens with my D50 and I was amazed at how poorly it focuses at close distances. I attached a friend's Nikkor 18-55mm to my D50 and it gets remarkably closer with the same item in focus. My assumption is that 18mm settings on two lenses with the same body should produce focus at the same distance. Am I wrong to assume this? What might be wrong with my 18-70mm lens then?