new guy with a d50 and some questions

hello there folks,

i have recently got a nikon d50 dslr with a nikkon af nikkor 35-80mm 1:4-5.6d lens
and although i am starting to get to grips with it i was wondering if some one can tell me why when i turn the lens to one of the numbers either 4 , 5.6 , 8 , 11 , 16, the camera say's error however when i leave the camera at 22 it works no problem

that is how these lens work for the aperature control by the camera! that is the auto mode, If you move it to Manual, it should be able to let you to set aperature, but really no reason to since in auto mode
you can change it via the command dial.

Lots of the older lens, actually allowed you to move a switch to lock it in the F22 so you don't accidently move it.